Carrington Event 1859 – Reconstructing Historical Space Weather Events

What is Space Weather and how does it affect us?

Space weather is the result of particles emitted by the Sun, termed the solar wind, interacting with the Earth's magnetic field. Large eruptions from the Sun, called Coronal Mass Ejections (CMEs), pose a hazard to the ground infrastructure, such as the high-voltage power network, in the form of Geomagnetically induced currents (GIC). GICs are excess currents in the power network that are created by the rapid variations of the magnetic field and in extreme cases have caused damage to transformers causing the power grid to temporarily shut down. These space weather events are the same natural phenomenon as those responsible for the Aurora becoming visible at mid-latitudes.

There are important questions about the hazard posed by space weather that are unanswered. These include:

• How big can geomagnetic storms be?

• How often do storms of this size occur?

• What is the series of events that can lead to the largest geomagnetic storms?

• What are the effects on modern technology?

  
  

What records do we have of historical geomagnetic storms?

The British Geological Survey (BGS) holds records for eight geomagnetic observatories operating in the UK going back to 1847. The digital era of geomagnetic observations began in the 1980s providing us with high-quality recordings of the Earth’s magnetic field but prior to this all data were recorded on photographic paper. The problem with the digital dataset is the dearth of very large geomagnetic storms. As shown in Figure 1, we have enjoyed an unusually quiescent era of solar activity since the 1960s.

Figure 1: Geomagnetic activity from 1880 to 2020, expressed by the daily Aa index. Figure produced as part of the British Geological Survey and the ESA Space Safety Programme (https://swe.bgs.ac.uk/bgs/indices.shtml?index=Aaindexdaily).

What is the Carrington Event?

These historical records contain some of the largest known geomagnetic storms including the famous Carrington event of 1st-2nd September 1859 – one of the large storms on record. The event and its lesser-known precursor were recorded at two rival observatories both operating in London at the time, Kew and Greenwich. This provides a great opportunity to cross-compare the two observatories only 20km apart.
The paper magnetograms provide a unique example of near-continuous measurements for the Carrington event and pre-cursor storm. We manually extracted the digital time series of Kew and Greenwich records of three components of vertical, horizontal and declination of magnetic field from 25-Aug to 05-Sep-1859 by digitizing the historic records. To assist with scaling the magnetograms into accurate time and magnetic units, we use published journal papers from the period to benchmark our interpretation and spot values recorded at Greenwich. This isn’t without its own problems, including:

• the poor quality of parts of the recorded traces

• overlap or missing traces

• Issues with instrumentation at the time of recording

• Lack of metadata to scale recorded traces to modern SI units of magnetic field.

Figure 2: Paper magnetograms recorded on photographic paper for observatories in London, UK. (a, b) Declination angle at Kew from 10:20UT 02-Sep-1859 to 12:05UT 05-Sep-1859 (c, d) Declination angle and Horizontal Force at Greenwich from 12:00UT 01-Sep-1859 to 12:00UT 03-Sep

Figure 3 shows the reconstructed time series of the magnetic field at both the Greenwich and Kew observatories. Reconstructing the days prior to the famous 1-2 September storms enables us to see the series of events that led to such an extreme geomagnetic storm. When storms occur in close succession, the first storm essentially clears the interplanetary space of solar wind and enables the subsequent storms to have greater impact on Earth. We can see evidence for a large storm during the 28th-30th storm for example. The period around August and September 1859 was unusually stormy compared to the modern era.

Figure 3: Digitized magnetograms of (a) horizontal magnetic field strength, (b) declination, (c) vertical magnetic field strength, at Kew (orange) and Greenwich (blue) observatories from 25- Aug to 05-Sep-1859. Highlighted green is the Carrington-observed flare at ~11:15-11:23 01 September 1859. Highlighted in grey are evidence for suspected earlier solar flares.

The analogue record is a rich and yet untapped source of information about geomagnetic activity in the past. With a more focussed effort and new digitisation tools, the community may be able to find better answers to the great unknowns of space weather hazards in future.

BGS Magnetograms: 
https://www.bgs.ac.uk/information-hub/scanned-records/magnetograms/

Authors:
E. Eaton¹, C. Beggan¹, E. Lawrence¹, E. Clarke¹, K. Matsumoto², H. Hayakawa^2
1British Geological Survey, ²Nagoya University

Eliot Eaton is a magnetotelluric field technician at the British Geological Survey, UK. His primary research focus is completing a magnetotelluric survey of England, Wales, and Southern Scotland to improve understanding of how geomagnetic storms influence the UK’s grounded infrastructure, such as the high-voltage power grid. During the COVID-19 pandemic, all fieldwork was postponed so he had the opportunity to dig into the historical geomagnetic archives of the UKs observatories.

Opportunities and challenges with palaeomagnetic data sources

In our quest to understand the geomagnetic field of past millennia, we rely on two primary sources of data. The first source is archaeomagnetic data, which provides us with valuable information about the geomagnetic field based on ancient artefacts. However, one major challenge we encounter is the uneven distribution of this data in both space and time. It's like trying to put together a historical jigsaw puzzle without all the pieces.

But don't worry, there is another data source that helps overcome these limitations and provides a more comprehensive understanding of the past geomagnetic field. Sedimentary records, a treasure trove of information spanning vast time periods and offering improved spatial coverage. Imagine these records as growing bars, each representing a time series of the geomagnetic field at a specific location. In contrast, archaeomagnetic data appears as dots, providing snapshots of the geomagnetic field at specific locations. As we venture further back in time, sediment data becomes increasingly essential since archaeomagnetic data becomes sparser.

The spatial and temporal data coverage.

Now let's unravel the different magnetization mysteries within these sediments. Archaeomagnetic data captures the geomagnetic field through a fascinating process known as thermoremanent magnetization (TRM). Picture this: ancient artifacts, like pottery and kiln structures but also lava flows are heated and then left to cool down. But here's the magical part - during this process, they become magnetized, preserving a snapshot of the geomagnetic field at that exact moment. It's like capturing a piece of geomagnetic field's history in a magnetic time capsule.

The magnetization process in sediments is known as detrital remanent magnetization (DRM). During the sedimentation process, magnetic particles settle in such a way that their magnetic moments tend to point in the direction of the geomagnetic field. It's like they have an ancient compass within them, pointing in the direction of the geomagnetic forces. With the accumulation of additional sediment material, the magnetic particles become mechanically fixed within the sediment structure, preserving their magnetic orientations. It's as if they have been frozen in time, capturing the magnetic field's influence at the lock-in moment.

The magnetization in sediments is influenced by several factors, such as the interaction between the magnetic particles and the substrate at the sediment-water interface (depositional DRM), as well as the consolidation and dewatering process of the sediment (post-depositional DRM). Within depositional DRM, various effects come into play. For instance, there is the inclination error, which arises when non-spherical particles settle flat on the sediment-water interface. This leads to a distortion of the inclination, resulting in smaller inclination values than expected.

In our investigation, we're particularly interested in unraveling the secrets of post-depositional DRM. Initially, only the larger sediment particles become mechanically fixed shortly after deposition. Smaller particles, on the other hand, enjoy a freer journey, moving within water-filled voids and pore spaces for a longer duration. However, as the sediment consolidates and dries out, these smaller particles slowly become locked in too. It's a mesmerizing process, like witnessing magnetic particles tell stories of the ever-changing geomagnetic field.

Check out the figure below that illustrates the journey of magnetic particles during the lock-in or pDRM process.

The sedimentation process.

A The lock-in adventure begins when the particles settle on the sediment-water interface. Sediments are composed of a mix of magnetic and non-magnetic particles, creating a vibrant playground. During the early stages of the lock-in process, particles rotate freely and align with the geomagnetic field. It's like a magnetic ballroom dance conducted by the geomagnetic field forces.

B As time passes and sedimentation continues, the surrounding material consolidates. Larger magnetic particles begin to lose their mobility and get locked in. They find their forever spots, holding onto the memories of the geomagnetic field at that time. But what about the smaller particles? They're still lively and free, closely following the twists and turns of the geomagnetic field.

C After ample sedimentation and consolidation, the lock-in process reaches its grand finale. Each particle becomes a storyteller, carrying a piece of the geomagnetic field's history within it. The sediment layer becomes a mosaic of magnetic moments, depicting diverse states of the geomagnetic field throughout the entire lock-in period. It's like a magnetic symphony composed of the melodies of the geomagnetic field.

The magnetic moment of a whole sediment layer represents a weighted average of the geomagnetic field over the lock-in period. This is where the concept of a lock-in function comes into play. The lock-in function assigns weights to the different geomagnetic field values, reflecting their significance during the lock-in process.

The investigation of the lock-in process and the development of a modeling concept to estimate the lock-in functions for individual core samples is the primary goal of our studies. Our research outcomes provide in-depth details, methodologies, and findings that shed light on the fascinating world of sediment records and post-depositional DRM. Visit https://sec23.git-pages.gfz-potsdam.de/korte/pdrm/ for more information. With our results we make sediment data a more reliable data source for modeling the geomagnetic field. It's time to unlock the secrets of the geomagnetic past!

Lukas Bohsung is a second year PhD student at the University of Potsdam and the Helmholtz Centre Potsdam — GFZ German Research Centre for Geosciences in Germany. His main focus is on investigating and modeling magnetization processes in sediments to make sediment records a more reliable data source for geomagnetic field reconstructions. He can be contacted via email here.

PhD in IAGA #6

IAGA has a lot of different scientists working on various topics. In this series of blogs, we introduce some topics that were or are being worked on by PhD students. Hopefully this will give a better picture of the work being done in the field and encourage more early career researchers.

Dr. Anita Devi completed her postgrad from the Department of Geophysics, Kurukshetra University, India after which she worked for two years as a Geophysicist in TVIPL. She did her Ph.D. from Indian Institute of Technology, Roorkee in 2019. For a brief period of 3 months, she also worked as a Post-Doctoral fellow (SERB-NPDF) at Wadia Institute of Himalayan Geology, India. During her doctoral research, she worked on various electrical and electromagnetic prospecting methods to deciphered resistivity structures. She is currently working as a Scientist at CSIR-NGRI, in magnetotelluric group. 

Her Ph.D. research was focused on 3D (3-Dimensional) individual and joint inversion of magnetotelluric (MT), Radio magnetotelluric and Electrical resistivity tomography (ERT) data. She presented the first 3D resistivity model for Garhwal Himalayan region around Roorkee-Gangotri and Chamoli region. She has worked on all the aspects of Magnetotelluric (acquisition, processing, 3D modelling and inversion). She is interested in delineating the 3D resistivity subsurface structures for exploration and tectonic studies. Her earlier work focuses on the geodynamic studies of Himalayan region. Currently she is working on 3D MT studies of both the Central Indian Tectonic Zone and the Himalaya region. She has published research papers in reputed national and international journals like Journal of Applied Geophysics and Near Surface Geophysics and participated in several International workshops (EMIW, IAGA-IASPEI).

Depth slices of the inverted 3D electrical model of Roorkee-Gangotri profile from Devi et al. 2019 with the letters marking the major resistivity features.

Training experiences: IAGA 2023 School

The IUGG Assembly that took place at Berlin from 11th to 20th July 2023 was preceded by the IAGA Summer School in Niemegk from 7th to 11th July. The school was organised by IAGA's ICEO - International Commission on Education and Outreach.

The participants were Early Career Researchers who got together at the magnetic observatory of Niemegk, Germany for theoretical and practical training in magnetism. There were 6 courses on various aspects of the magnetic field such as core and crustal fields, electromagnetic induction, and numerical as well as observational modelling among others. The 25 participants hailed from 15 different countries spread over the globe. Some testimonies of their experience are below-

Manu Varghese: IAGA summer school 2023 was my first in-person summer school, and the experience was really amazing! I met fellow students and researchers from different parts of the world. We discussed our research areas and I feel like such interactions open the way for future collaborative research and friendships. I also found lectures other than my focus area understandable since the professors started from first principles and their approach was well rooted in fundamental principles. Niemegk observatory, Germany is a place of long tradition in measuring the geomagnetic field and the observatory itself possesses a valuable set of archives. The visit to the observatory enlightened the path forward for my research.

Frederik Madsen: It was such a great experience, both to get a better understanding of the different aspects of the geomagnetic field, as well as being in the place where data is recorded, but also to make friends from all over the world - friends who may very well be my future colleagues. We all study different parts of the geomagnetic field, so in a sense, we’re all becoming experts in each other’s noise. It was really valuable to get such deep insight from people who are really passionate about the different features of geomagnetism. I'm very grateful for having had this experience - the 198 mosquito bites was definitely worth meeting such wonderful people!

Miroslav Hanzelka: The IAGA summer school was a great opportunity to meet with young scientists working on topics across the whole range of IAGA disciplines, something I don't usually experience during narrowly focused conference sessions. As someone who recently finished their Ph.D., hearing from the other students and post-docs about how Ph.D. research works in different countries helped me broaden my horizons. The hosts at the Niemegk observatory gave us a tour around the facilities, letting us see the history and present of geomagnetic field measurements in Germany. Many of the school organizers and lecturers were available even outside of the scheduled program, happy to discuss their work and give research tips to the students. The overall atmosphere at the IAGA school was very friendly and laid-back, thanks to both the organizers and the relaxed ambience of German villages. Would attend again :)

Nitin Kadam: My IAGA summer school experience was very transformative and enlightening. I gained valuable insights and connected with like-minded peers. The brainstorming lectures and hands-on activities (more specifically during the paleomagnetic sessions) provided a deeper understanding of the topics. The experience has undoubtedly enriched my academic journey and broadened my perspective.

Space News

The Voyager 1 and 2 satellites were launched in 1977 to study and understand the giant planets of our
Solar System. It provided the first and only measurements yet around the two ice giants - Uranus and Neptune. However, the mission didn't end after that. The two satellites are still operating far beyond the giant planets in interstellar space.

The interstellar space starts where the Sun can no longer affect the surroundings. Voyager 1 entered this region in August 2012 while Voyager 2's entry was in November 2018. Their present distances from Earth are about 23 and 19 billion kms respectively. But a few days ago, NASA lost communication with Voyager 2 due to a shift in antenna. Hopefully, they can get it back by October when the satellite next resets itself for orientation. The mission also has a twitter account to keep us updated about news beyond the Solar System.

Lastly, we leave you with an interesting image from Voyager 1 taken at a distance of about 6 billion kms (from the Sun) called 'The Pale Blue Dot'. Try to find the Earth here. Hint: Look at the bright scattered light near the right of the image. It shows just how unimportant we are in the vast expanse of the universe. A reminder to not take ourselves and others too seriously! 

Images Credit: NASA

Early Career Researchers at IUGG '23

The International Union of Geodesy and Geophysics (IUGG) recognises the Early Career Scientists (ECS) upper limit as people who completed their PhD 10 years back. For all the ECS, there was a registered social event that took place at the IUGG General Assembly in Berlin on 15th July 2023. It was the first of its kind event with participation from all the 8 associations of IUGG working on different sciences. 

The ECS social evening was attended by more than 200 people spread across all the associations. After a long break from online conferences due to the pandemic, everybody was quite happy to interact face-to-face. Scientists early in their career got the chance to meet and interact with other scientists working on a different domain in a different country. The highlight of the event was a set of 10 questions related to their fears and academic lives that was to be discussed in a panel session the next day. Some pertinent questions were raised in hopes of the associations recognising and solving these problems. The attendees also had the opportunity to give suggestions and ask questions to IUGG.

Poll results from two of the ten questions asked to the Early Career Researchers in the social evening. Credit: Jamie Farquharson

The next day, at the Big Themes panel discussion, each of the association had a representative who tried to answer the poll results and raise the awareness and concerns of their association to IUGG. It was an hour long open discussion which was attended by both ECRs and established scientists.

The representatives and organisers of each of the 8 IUGG associations with the IUGG Secretary General at the Big Themes panel discussion on July 16th, 2023 in CityCube Berlin. Credit: Jan Pauls

This event was the starting point of a hopeful long association between IUGG and its ECR's needs, wishes and demands. Hopefully, in 4 years, in the next IUGG Assembly in Incheon, Korea, some of these problems will no longer exist or will be partially solved.

IAGA Social Media meetings in IUGG

The IUGG General Assembly is finally here! The sessions for IAGA happen between 13th and 18th July in CityCube Berlin. Specifically, the social media has a lot of sessions happening in IUGG. If you are a registered candidate, you are welcome to attend any and all of them!

14th July 2023

Business meeting of IAGA Interdivisional Commission on Education and Outreach with Social Media WG - 18:00 to 19:30 CEST in Hall M5

15th July 2023

Session JH06b (morning) - Bimbim's Team: A journey to the planets - 10:30 to 10:45 CEST in Hall A3

Session JH06b (afternoon) - Geoscience Connections - 13:45 to 14:00 CEST in Hall A3

Session JH06b (afternoon) - Content Creation from the IAGA Social Media Working Group - 14:00 to 14:15 CEST in Hall A3

See you at IUGG in our sessions!