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12th Hel.A.S Conference
Thessaloniki, 28 June - 2 July, 2015
Correlation between Solar Energetic Particle events and
Earth’s surface Temperature in North-East USA
G. Anagnostopoulos1, S.A. Menesidou1, V.G. Vassiliadis2* and A. Rigas1
1Department of Electrical and Computer Engineering,
Democritus University of Thrace,
2IBM Research Zurich
Abstract: The influence of space weather on the Earth’s atmospheric weather and climate is an
important scientific issue with great social interest. In this study we present, for the first time, statistical
results during times of 28 strong ICMEs observed between 1997 - May, 2015, which confirm a strong
correlation between the solar activity and the temperature TMin east USA (Madison, Wisconsin). In
particular we found that: (a) during a time period of 15 days (day=-7 to day=+7) centered at the
day D0of ICMEs arrival at Earth, the temperature (TM) in Madison shows maximum values around
(+/- 1 day) or after the day D0in 89.2% of the cases examined, (b) the high (1880 - 4700 keV) energy
solar proton (HESP) fluxes, show a much stronger correlation with TMthan the magnetospheric 68 -
115 keV ions and 38 - 53 keV electrons, before the ICME arrival, (c) the temperature increase reached
on day D0is strongly (r= 0.8, p < 0.001) correlated with the time duration of the HESP events, (d)
the temperature increase during the cases examined is very strongly and significantly correlated with
the HESP flux increase, within ∼1 day (r= 0.9, p < 0.001) (e) warm air flows from the southward
direction mediates the link between HESP fluxes and the temperature increase ∆TM, and (f) the
temperature increase ∆TMduring the HESP events shows an average rate of ∼2◦C/day (28 events
examined). We infer that the HESP events preceding the great ICMEs examined in this study strongly
control the temperature TMin east USA during the “winter” times, via a fast (∼1 day) process due
to northward air flows from the Gulf Stream.
1 Introduction
“A growing mass of evidence suggests that transient events on the Sun affect our weather and long-
term variations of the Sun’s energy output affect our climate. Solar terrestrial exploration can help
establish the physical cause and effect relationships between solar stimuli and terrestrial responses.
When these relationships are understood science will have an essential role for weather and climate
prediction.” This statement was a part of an early proposal of R.D. Chapman submitted to NASA [1].
Since those times, and in particular the two last decades, an amount of evidence has been gathered on
links between Solar activity and variations in the Earth’s ionosphere and atmosphere. Further advances
in the prediction of Weather/Climate changes could help people’s health and life, in particular during
atmospheric extreme events, which have some dependence on space weather [2, 3].
There are many reports from the beginning of space era suggesting a correlation of solar flares
with pressure gradients in atmosphere, within 2-3 days or less (<6h) [4]. In the last two decades,
great emphasis has been given in the solar cycle climate trends of cloudy, stratospheric changes, polar
temperatures and winds, as well as the sea and surface temperature [4]. Most of these meteorological
variations have been discussed in terms of solar irradiance as a stimuli, but recently energetic particle
forcing driving dynamical changes in the atmosphere were suggested to be as intense as those arising
from the solar irradiance variations [5]. In these studies, the solar particles were considered to affect
the atmosphere via a slow process of catalytic ozone destruction. However, in a recent study for
*Work conducted while at Democritus University of Thrace
1
ANAGNOSTOPOULOS ET AL: Correlation between SEP - Western USA Temperature
Figure 1: Time profiles of (a) temperature at Madison, Win-
sconsin (b) the direction of wind in the same town, (c) the
fluxes of energetic proton and electrons observed by the ACE
spacecraft and (d) the values of the geomagnetic index Dst,
during March 3-31, 2015. It is evident that the temperature
TMprofile (panel a) resembles that of the high energy solar
proton flux P8 (red curves).
Figure 2: The estimates of the cross-
correlation coefficients r for lags k=
0,±1,...,±7, between the daily values
of the logarithm of the P8 proton flux
values and the temperature TMfrom
day 6 until day 16, March 2015. The
solid black lines present the asymptotic
95% confidence limits of the estimated
coefficients. The very large r value at
lag=0 confirms and explains the good
resemblance of P8 and TMcurves seen
in Figure 1.
the March 2012 superstorm [2], the solar and magnetospheric particle events were found to control
extreme weather events all over the globe, and in particular the historic March 2012 heat wave in
East USA/Canada, via a fast (∼1) day process [3]. During that Solar Energetic Particle (SEP) event
solar protons of very high energy (0.6 GeV), were observed by PAMELA spacecraft, which seem to
strongly influence the atmospheric conditions (Anagnostopoulos et al., 2015; paper to be published).
In this paper we present statistical results which strongly support the hypothesis that high energy
(1880 - 4700 keV) solar protons arriving at Earth’s environment during solar activity strongly affect
the surface temperature in the north-east USA, via a fast processes, within ∼1 day.
2 Data Analysis
In order to check the possible permanent link between the high solar activity and the temperature
in north-east USA, we selected the ICME-related storms/superstorms with Dst index value as low as
Dst ≤ −150nT , from the beginning of ACE mission (1997) until May, 2015. By using a catalogue
of ICMEs [http://www.srl.caltech.edu/ACE/ASC/DATA/level3/icmetable2.htm], we found 28 HESP
events meeting the criteria of our study and we made full analysis for 26 events, due to data gap of
2 events. Then we compared the possible correlation of the HESP events observed by EPAM/ACE
[http://www.srl.caltech.edu/ACE/ASC/level2/lvl2DATA EPAM.html] before the arrival of the ICMEs
with the temperature history at Madison, Wisconsin.
In Figure 1 we present a representative HESP event from the list of the 28 events examined. In
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ANAGNOSTOPOULOS ET AL: Correlation between SEP - Western USA Temperature
Figure 3: Distribution number of SEP
events with time delay ∆τbetween the
days of maximum temperatrue in Madi-
son TMand the maximum high en-
ergy solar proton flux P8, during a pe-
riod of 15 days centered at the day of
the ICME. The large number of non-
negative values suggests that the maxi-
mum temperature TMcoincides with or
follow the solar proton manixmum P8.
Figure 4: Surface temperature increase ∆TMduring SEP
events as a function of their time duration ∆τ, during “win-
ter” (a) and “summer” times (b). During “winter times”, a
strong and very significant (r= 0.8, p < 0.001) correlation
was estimated.
particular, Figure 1 shows time profiles of the daily maximum value of temperature TMat Madison
(panel a), the direction of wind in the same town (panel b), the fluxes of energetic (38-53 keV; DE1
channel) electrons, and of both low (68-115 keV; P1 channel) and high (1880-4700 keV; P8 channel)
energy protons arrived from the sunward direction observed by the spacecraft ACE outside the Earth’s
magnetosphere (panel c) and the geomagnetic index Dst (panel a), for the time period March 3-31,
2015; the time series of Figure 1 have been centered around the time of the severe (G4) storm of March
17 which was triggered by the most intense CME of the solar cycle 24 (notice that the Dst index
reached values on day 17, as low as -223nT).
By comparing the profiles of the ACE energetic particle flux profiles with the profile of temperature
TM, we see: (a) a good similarity, in particular, between P8Mand T profiles and (b) a gradual increase
of both P8 flux and TMvalues from day 6 until day 16 (the day before the ICME arrival). Further
comparison between panels a-c and b demonstrates that during the time of the gradual increase of
energetic protons at ACE and the temperature at Madison, the wind shows a flow from the southward
direction (days 6-16; red great rectangular in panel b). On the contrary, we see that before day 6 (days
4-5) and after day 16 (days 17-19), both the P8 proton flux and the temperature TMat Madison show
low values, which were accompanied by air flows from northern directions (green rectangulars). The
above data suggests a good correlation between the flux of HESP and the temperature at Madison
before the ICME of March 17, 2015, which was observed during a warm air transfer from the Gulf
Stream.
In Figure 2 we present the estimates of the cross-correlation coefficients between the logarithm of the
P8 proton flux values and the temperature TMfrom day 6 until 16 (Fig. 1) and for lags 0,±1,...,±7.
The upper and lower confidence limits are denoted with solid black lines. We found a very significant
positive correlation at lags -1, 0 and 1. Especially at lag = 0 the cross-correlation coefficient takes
its maximum value r = 0.907 with s.e. = 0.277(p < 0.001). This indicates that one should notice an
increase of the temperature TMfrom the previous day till one day after of an analogous increase of
the proton flux. The very large r value at lag = 0, confirms and explains the day to day simultaneous
resemblance of the line plots of the temperature TMand the P8 proton flux at Figure 1 (a, c).
Figure 3 shows the distribution number of the 28 SEP events with a time delay ∆τbetween the day
of the maximum temperature TMat Madison and the day of the maximum solar proton flux P8, within
a time interval of 15 days centered on the day of the ICME arrival. Positive (negative) values of delay
time ∆τmeans later (earlier) recorder of maximum temperature TMthan that of the maximum solar
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ANAGNOSTOPOULOS ET AL: Correlation between SEP - Western USA Temperature
flux P8. From Figure 3 we see that the majority of events show non negative values, which suggest
that maximum surface temperature coincides (∆τ= 0) with or follow (∆τ > 0) the solar proton flux
maximum P8.
In Figure 4 we present scatter plots of the total temperatures increase ∆TMversus the time duration
of the P8 proton flux increases before the ICME arrivals, for winter times (October to April; panel a)
and in summer times (May - September; panel b), respectively. Panel a shows a very strong correlation
(r'0.8), between ∆TMand ∆τ, which is very significant (p < 0.001). A linear interpolation shows
a trend b'2, which suggests an average daily temperature increase in Madison before great ICME-
related storms during winter times ∆TM/∆τ= 2◦C/day. From panel b we infer the absence of any
significant correlation between ∆TM−∆τduring the “summer times”; furthermore, we see that lower
temperature increases ∆TMwere in general recorded during the “summer” times (panel b) compared
to the temperature variations during “winter” times.
3 Conclusions and Discussion
The main finding of this study is a strong and statistically significant correlation between the
temperature increase ∆TMat Madison/Wisconsin with the time duration of the HESP events before
the arrival of ICMEs between 1998 - May 2015, during months October to April. A second result
is that this correlation happens under atmospheric conditions of warm air flows from the southward
direction, which are obviously related with the Gulf Stream.
Several physical mechanisms have been proposed in order to explain some links between high solar
magnetosphereric activity and SEP event, with changes in atmospheric conditions. Such mechanisms
include SEP relation with large stratospheric/tropospheric pressure gradient causing downward air
flow, variation in the global electric circuits and stratospheric ozone-related chemical energy changes
[1]. Since our results of the present study indicated a fast correlation (of the order of ∼1 day; Figure
2), the catalytic ozone destruction, which is a slow process, should not be the major driver of the SEP
related temperature variation in north-east USA (Wisconsin).
The results of the present statistical study suggest that the south air flow mediates the influence of
SEP events with the surface temperature variations (increases in north-east USA). Here we note that
during the last great ICME of March 2015, the temperature TMincreased from -9◦C up to as high
as 23◦C (an increase of 32◦C), within only 10 days (6-16 March, 2015) which suggests a very effective
process in this case. The question tp be addressed is which is the physical link between the early
SEP impact and the intensification of the warm Gulf stream. Although this question needs further
examination, we note the following known physical phenomena: (1) a solar cycle periodicity of the Gulf
Stream activity [6], (2) a correlation between SEP activity and the North Atlantic Oscillation (NAO),
and (3) a correlation between NAO index and the sea surface temperature in the east USA [7]. These
results may suggest a physical link between SEP flux increase / NAO index variation / Gulf stream
intensification south warm air flows and temperature increases in east USA. Finally, we note the fast
(within ∼1 day) response of TMto HESP variations, which rather suggests that a non-linear process
controls the sequence of physical variations described above.
Acknowledgements: The authors thank Dr L. Lanzerotti for providing the ACE / EPAM ener-
getic particle data and they acknowledge the use of meteorological data from WeatherOnline Online
Services and geomagnetic data from the World Data Center for Geomagnetism, Kyoto. The authors
also acknowledge the ICME list provided by Dr Ian Richardson. This study was supported by the
NSRF 2007-2013 Thales - Hellenic National Network for Space Weather Research (HNSWRN) - MIS
377274 project of the Greek Ministry of Education, Lifelong Learning and Religious Affairs - General
Secretariat for Research and Technology.
References
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ANAGNOSTOPOULOS ET AL: Correlation between SEP - Western USA Temperature
[2] Hoerling M., Meteorological March Madness 2012, NOAA,
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http://presentations.copernicus.org/EGU2015-14048 presentation.pdf, 2015.
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[6] Taylor, H., North - South shifts of the Gulf Stream and their climatic connection with the abundance
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