1. The document summarizes research analyzing low frequency ground signals detected during solar flares to determine their source. 2. Two 1997-1998 events showed ground signals coinciding with solar radio bursts and x-ray flux. 3. However, subsequent analysis of over 300 solar flare events at 3 Arctic sites from 2006-2014 found no clear association between low frequency ground signals and solar radio bursts or flares.

1. I would like to thank Professor James LaBelle and Sarah McGregor for great guidance and help,
also Women in Science Program for funding and for providing the valuable opportunity to do
research works in the field of physics.
• Further exploration of Methodology #2 by analyzing type iii d events for Churchill,
Sondrestrom, and Toolik.
• Review older data (from the 90s) to anticipate another possible cause.
• Analysis of the effect of solar angles on the correlation between ground level low frequencies
and type iii d.
1.Solar wind might be the cause of the ground low frequency signals instead.
2.Adjust the C program to look for the type iii d “spikes” that happen during sunlit
time for South Pole.
3.Check the ground level radio signal spectrogram to look for low frequency that
coincide with type iii d.
4.Check the corresponding x-ray flux to confirm its association with strong solar flare.
5.For further analysis on the effect of solar wind intensity, identify the intensity of all
the selected “spikes” and compare with the two exemplar events.
Sites Checked:
South Pole, Antarctica Churchill, Manitoba Sondrestrom, Greenland
Statistics
•X-ray flux for a specific event is checked only when
possible ground level signal is found.
•However, none of the possible events coincident with
type iii d radio burst in the way that the two events
from 1997 and 1998.
•Results suggests that the low frequency signal
detected from ground based instruments might not
be caused by strong solar flares or by itself alone.
Solar flares are sudden flashes of radiation from the Sun, covering an immense wavelength range:
from radio waves to gamma-rays. They release a huge amount of energy, between 10^19 and
10^25 J, which is partially spent in heating and accelerating particles. They are index of high solar
activity, being much more frequent during maximum of 11-year sunspot cycle.
Major fractions of the flare-accelerated electrons and protons escape into space, guided by the
magnetic field lines that are carried out into the heliosphere by the evolving solar wind. Injections
of electrons in the keV energy range are accompanied by radio wave emission with frequencies
from MHz down to kHz. These are called the type iii radio bursts.
Two events of ground based signals coincident with x-ray flux and wind initial high
frequency part of solar type iii radio emission were identified from 1997 and 1998. However, the
low frequency (below 1 MHz) part that happened right at the time of the burst in no way should
be observed by these ground based instruments. Because low frequencies are blocked by
the ionosphere.
Theoretical analysis suggests that this phenomenon is not caused by instrumental errors because
1000x solar type iii amplitudes would be required.
Both events were observed at sunlit observatories.
Search for Radio Phenomenon Associated with Strong Solar Flares
Suey Chen, Advisors: James LaBelle, Sarah McGregor
Department of Physics, Dartmouth College
RESULTSMODELS
INTRODUCTION METHODOLOGY #1
FUTURE DIRECTIONS...
ACKNOWLEDGEMENTS
METHODOLOGY #2
1. Both of the two events happened during strong solar
flares.
2. Select only the flares of strong M and X
that happen during the sunlit time of each of
the 3 sites for years 2006 to early 2014
by using a C program.
3. With the list of selected flares, check the
ground level radio signal for low frequency
signals at the time that a flare also happened.
4. If possible event is founded, check if a solar
type iii D signal is also detected.
Location: Antarctica
Date: 11/06/1997
Ground level radio signal spectrogram,
GOES x-ray flux, and Solar type iii D.
Location: Arviat, NWT
Date: 05/02/1998
Ground level radio signal spectrogram,
GOES x-ray flux, and Solar type iii D.
Location: Churchill, Manitoba
Date: 01/20/2010
Ground level radio signal spectrogram,
GOES x-ray flux, and Solar type iii D.
One of the possible events is shown on the right. We
analyzed it by following the same strategy we used for
finding and two events from 1997 and 1998.
Its frequency range is approximately from 2000 kHz to
2900 kHz. It coincides with a peak of x-ray flux, which
shows that the solar flare that happened at that time
reaches the M class.
However, when we look at the the solar wind data for
this time period, there is no type iii d flare burst.
Location Churchill Sondrestrom South Pole
Checked 32 33 227
Ground
Level
Signal
3 2 6
X-ray
Flux
3 2 6
Type iii D 0 0 0
Site Checked:
South Pole, Antarctica
RESULTS
The intensities of the Nov 6
and the May 2 events are
160 and 110, respectively.
In contrast, the intensities
of the type iii d that happened
during sunlit time of South
Pole are relatively low.
With 38 out of 44(86%) below
intensity of 21.
Therefore the low frequency
radio signal could be caused
by high intensity type iii d.
• Total of 44 solar type iii d “spikes” were checked for South Pole. Compared to the 227 events
from Methodology #1.
• Many of these happened during a M or X solar flare.
• No prominent ground radio signals coincide with the solar type iii d.
Program written for selecting solar flares for
theoretical criteria.