The Signature of the March 31, 2001 Geomagnetic Storm

in Aurora Dx Communication on Very High Frequencies

Actual results of a data analysis project in ham radio

Volker Grassmann, DF5AI

Last update: June 01, 2005

Introduction

Note: Readers not yet familar with amateur radio propagation studies are requested to read this special introduction first: more ...

There is a long history of Auroral backscatter analyses using amateur radio observations on very high frequencies (see, e.g., [1], [2]-[5], [26], [27], [28], [31], [35]). On the other hand, no analysis has yet considered simultaneous Auroral backscatter observations from radio amateurs located in different continents. Geomagnetic storms represent global events, we may therefore conclude that Aurora dx openings develop on a global scale too. This assumption is supported, for example, by the dx reports distributed by the dx cluster networks: having identified an Aurora dx opening in the European sector, the dx cluster also provides information on dx QSOs in North America, and vice versa. The regional characteristic of Aurora dx openings is indeed well known, we however lack detailed information when considering Aurora band openings from a global perspective (note: when using the term global we actually focus on polar and mid-latitudes, excluding equatorial regions because Auroral backscatter is not available there).

About this project

In this project, we will analyse the global characteristics of Aurora dx communication associated with a major geomagnetic storm. Initially, a number of recent storm events was taken into consideration when preparing this project - it is the March 31, 2001 event which was finally selected here. That choice results from the requirements in data acquisition, i.e. this event can provide sufficient material from radio amateurs and from scientific internet resources as well.

The project separates into individual work packages allowing the author to organize data acquisition, data analyses and discussions in modular tasks. The reader is therefore confronted with an ensemble of living documents which may change look and content depending on the actual progress (all documents therefore show an individual date information in the header).

Please note, that the documents deal with two types of references, i.e. numbers in brackets and highlighted text, respectively. For example: the reference [10] denotes material which is explicitly used in this document, see the list of references at the bottom of this page. Terms such as solar wind, on the other hand, denote hyperlinks to general background information available in the internet. The reader may visit this internet locations to access additional information from professional web sites edited by experts and scientists.

Outlook and actual results

• For the first time, we may study Aurora dx openings in Europe, North America and Australia associated with the same geomagnetic storm event.
• For the first time, we may directly compare ham radio observations with NASA's POES satellite data.
• For the first time, we can document the correlation between Aurora dx openings and the actual direction of the interplanetary magnetic field (IMF).
• We will introduce an innovative data analysis method which can locate the geographical position of Aurora backscatter without using antenna headings or any other type of directional information.
• The dx range of the 50 MHz Aurora QSOs is very similar to the 144 MHz QSOs - the dx range of 432 MHz QSOs is significantly shorter.
• Analysing the distribution of the QSO distances in Europe, all radio frequencies show the same unusual dx maxima which cannot be explained.
• The average QSO distances in North America appear shorter than in Europe for an unknown reason.
• Accidental result or real effect: radio propagation paths in the north-south direction appear temporarily extinguished.
• ... (more to come?)

Project structure and work packages

The following paragraphs provide an overview on the individual work packages which are organized in three main categories, i.e. organizational aspects, data acquisition and data analysis methods and, finally, the result section, respectively. The author appreciates comments, suggestions and ideas at all times. This project may be considered an open project, i.e. radio amateurs wishing to suggest alternative methods of data processing, special analyses and creative concepts in data visualization are requested to contact the author by email, see the box on the right.

Contact

To contact the author, please follow this link.

Objectives & organisation

Because of the huge amount of data, this project requires some sort of organizational framework. View the project's objectives, the road map and the actual status report. More...

objectives

Data acquisition, tools and analysis methods

This project received special support from the POES team at NASA that has contributed a sequence of data files documenting the Auroral activity on March 31, 2001. Information on more than 3.800 Aurora QSO was obtained in the data acquisition phase between December 2002 and May 2003. Eliminating double counts, the analysis now considers around 2.200 Aurora QSOs. The European sector contributes around 1.900 QSOs, 240 QSOs originate from North America and 21 from Australia. The data covers the observation period from 0010 UT to 2356 UT on March 31, 2001. More...

data acquisition

Number and data crunching software tools are most important in this data analysis project, of course. The BeamFinder software will in particular play an important role here because it can easily handle thousands of QSOs and it can analyse the individual backscatter geometry of all dx QSOs. More...

tools

Reliable information on the dx stations' actual antenna heading is not available, i.e. we cannot locate Aurora positions by applying the geometrical method of triangulation. In this analysis, we will therefore refer to an innovative method which can estimate Aurora positions without using antenna headings or any other type of directional information. More...

locating Aurora

Data analysis, results and interpretation

On March 28, 2001, a coronal mass ejection (CME) near the active sunspot region 9393 hurled a high-speed solar wind stream of electrified, magnetic gas towards the Earth. On March 31, 0053 UT, this shock front pushed into the dayside magnetosphere causing geomagnetic field disturbances and other types of phenomena including wide spread Aurora band openings on very high frequencies. More...

storm history

The sequence of POES data plots has been assembled to an animated view of the Auroral activity in the northern hemisphere. Watch the Auroral oval rotating around the geomagnetic pole and see the variation of the hemispheric input power during the day. A broadband internet connection is recommended to load the animation (1.7 megabytes) in reasonable time. More...

Auroral activity

An impressive correlation was found between the QSO data and the actual direction of the interplanetary magnetic field (IMF) - which is no surprising result but it is this project that documents the feature for the first time. More...

IMF

The intensity of Auroral backscattering shows significant fluctuations which are also present in the QSO activity, of course. 50 percent of the QSO data has been contributed by 90 percent of the stations, i.e. the second half of the QSO data originates from only 10 percent of the stations. More...

operational results

To compare the POES satellite data with the QSO data, the POES polar plots have been transfered to BeamFinder's Maidenhead grid locator map together with the Aurora QSO data from VHF radio amateurs. A broadband internet connection is recommended to load the animation (2.1 megabytes) in reasonable time. More...

POES vs. QSOs

The distribution of QSO distances shows two unusual maxima in the European sector which cannot be explained. In North America, the distribution is shifted to shorter paths lengths for on unknown reason. More...

QSO distances

... to be continued

Acknowledgements

The author is grateful to D. Evans and S. Greer (NOAA/POES) and Dr. Phillips (Science@NASA, SpaceWeather.com) for providing scientific background data. Many thanks also to A. Kantola (OH2AQ DX Cluster), the Dubus magazine, 9A1CAL, DD0VF, DF2ZC, DG3GAG, DG9MAQ, DH0GHU, DK1GS, DK1KO, DK3XT, DK5YA, DL1EJA, DL1ELY, DL1SUZ, DL2FDL, DL2OM, DL6WU, DL6YEH, DL8HCZ, DL8LAQ, DL9YBZ, DM2DXG, G0AEV, G1OGY, G3LTF, G3UYM, G3YYD, G4ASR, G4IFX, G8HGN, GM0ONN, GM4AFF, GW8IZR, HA6NN, HB9DFG, I1JTQ, I3LGP, I5WBE, IK2YXK, IZ1BPN, LA0BY, LA3BO, LY2SA, OE1SOW, OE3FVU, OE3MWS, OH1HSC, OH5LK, OH5IY, OH6FX, OH6MAZ, OK1TEH, OK2POI, OK2PM, OM5UM, ON4LN, OY9JD, OZ4VW, PA4VHF, PA5DD, PE1HWO, RK3AF, S53VV, SP2IQW, SP4MPB, UA3TCF, VE5UF, VK3AFW, VK3BJM, VK3CAT, W0VB, W3ZZ, W8WN, W9JN and M. Farrell for providing observation data and valuable assistance.

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