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Multi-Instrument Observations of a Geomagnetic Storm and its Effects on the Arctic
Ionosphere: A Case Study of the 19 February 2014 Storm
Observations of a Geomagnetic Storm
Durgonics, Tibor; Komjathy, Attila; Verkhoglyadova, Olga; Shume, Esayas B.; von Benzon, Hans-Henrik;
Mannucci, Anthony J.; Butala, Mark D.; Høeg, Per; Langley, Richard B.
Published in:
Radio Science
Link to article, DOI:
10.1002/2016RS006106
Publication date:
2017
Document Version
Peer reviewed version
Link back to DTU Orbit
Citation (APA):
Durgonics, T., Komjathy, A., Verkhoglyadova, O., Shume, E. B., von Benzon, H-H., Mannucci, A. J., Butala, M.
D., Høeg, P., & Langley, R. B. (2017). Multi-Instrument Observations of a Geomagnetic Storm and its Effects on
the Arctic Ionosphere: A Case Study of the 19 February 2014 Storm: Observations of a Geomagnetic Storm.
Radio Science, 52(1), 146–165. https://doi.org/10.1002/2016RS006106
This article has been accepted for publication and undergone full peer review but has not
been through the copyediting, typesetting, pagination and proofreading process which may
lead to differences between this version and the Version of Record. Please cite this article as
doi: 10.1002/2016RS006106
© 2016 American Geophysical Union. All rights reserved.
Multi-Instrument Observations of a Geomagnetic Storm and its Effects on
the Arctic Ionosphere: A Case Study of the 19 February 2014 Storm
Tibor Durgonics*
1,2
, Attila Komjathy
2,3
,
Olga Verkhoglyadova
2
,
Esayas B. Shume
2,4
,
Hans-Henrik Benzon
1
,
Anthony J. Mannucci
2
,
Mark D. Butala
5
,
Per Høeg
1
, and
Richard B. Langley
3
1
Technical University of Denmark, National Space Institute (DTU Space), 327-328
Elektrovej, Kongens Lyngby, Denmark.
(e-mail: tibdu@space.dtu.dk)
2
NASA Jet Propulsion Laboratory, 4800 Oak Grove Dr, Pasadena, CA, USA.
3
Dept. of Geodesy and Geomatics Engineering, University of New Brunswick, Fredericton,
N.B., Canada.
4
Astronomy Department, Caltech, Pasadena, CA, USA.
5
University of Illinois at Urbana-Champaign, Champaign, IL, USA.
Abstract
We present a multi-instrumented approach for the analysis of the Arctic ionosphere during
the 19 February 2014 highly complex, multiphase geomagnetic storm, which had the largest
impact on the disturbance storm-time (Dst) index that year. The geomagnetic storm was the
result of two powerful Earth-directed coronal mass ejections (CMEs). It produced a strong
long lasting negative storm phase over Greenland with a dominant energy input in the polar-
cap. We employed GNSS networks, geomagnetic observatories, and a specific ionosonde
© 2016 American Geophysical Union. All rights reserved.
station in Greenland. We complemented the approach with spaceborne measurements in
order to map the state and variability of the Arctic ionosphere. In situ observations from the
Canadian CASSIOPE (CAScade, Smallsat and IOnospheric Polar Explorer) satellite’s ion
mass spectrometer were used to derive ion flow data from the polar cap topside ionosphere
during the event. Our research specifically found that, (1) Thermospheric O/N2
measurements demonstrated significantly lower values over the Greenland sector than prior
to the storm-time. (2) An increased ion flow in the topside ionosphere was observed during
the negative storm phase. (3) Negative storm phase was a direct consequence of energy input
into the polar cap. (4) Polar patch formation was significantly decreased during the negative
storm phase. This paper analyzes the physical processes that can be responsible for this
ionospheric storm development in the northern high-latitudes. We conclude that ionospheric
heating due to the CME’s energy input caused changes in the polar atmosphere resulting in
N
e
upwelling, which was the major factor in high-latitude ionosphere dynamics for this
storm.
Index terms: Auroral ionosphere, Ionospheric disturbances, Ionospheric dynamics,
Ionospheric storms, Polar cap ionosphere
Keywords: Total electron content, Scintillations, GNSS, Ionograms, Geomagnetic storms,
High-latitude ionosphere
1. Introduction
In this paper we focus on ionospheric storm disturbances in the Arctic ionosphere. The
impact of geomagnetic storms on the ionosphere and the underlying first principles behind
these physical and chemical processes have been discussed by numerous authors, including,
© 2016 American Geophysical Union. All rights reserved.
e.g., Rodger et al. [1992], Buonsanto [1999], and Blagoveshchenskii [2013]. Nevertheless,
the precise geophysical background behind this complex system is still not completely
understood [e.g., Lastovicka, 2002]. Coronal mass ejections (CMEs) and other
manifestations of solar activity can trigger magnetospheric storms that may cause global or
regional geomagnetic disturbances impacting the ionosphere. These effects will result in
changes in the regular (e.g., diurnal, seasonal) ionospheric processes [e.g.,
Blagoveshchenskii, 2013; Durgonics et al., 2014].
Interaction between a CME and the magnetosphere often starts with the arrival of a shock
wave in near-Earth space. On Earth’s surface the outset of such interaction is seen as the
sudden impulse (SI), which can be detected using, for example, geomagnetic field horizontal
(H) component measurements collected by magnetometers. There is a set of well-established
indices to identify the early stages of these interactions including the global disturbance storm
time (Dst) index [e.g., Anderson et al., 2005; Le et al., 2004; Blagoveshchenskii, 2013], or
the regional auroral electrojet (AE) index which is derived from auroral region magnetic
stations and the polar cap north (PCN) index computed from a near-pole single magnetic
station (details on the indices can be found in, e.g., Wei et al. [2009] and Vennerstrøm et al.
[1991]). A sudden decrease in the Dst values typically indicates a change in the globally
symmetric and asymmetric (partial) components of the ring current suggesting a global
geomagnetic event [Liemohn et al., 2001]. Once such an event is identified, the local state of
the geomagnetic field can be observed using data from the individual magnetic observatories
in the Arctic region. The localized measurements can provide additional insights into the
electromagnetic response to storm input, since the Dst is derived from a global network of
stations with local information content no longer overtly present. These observed magnetic
disturbances indicate dependence on the quasi-dipole (QD) coordinates [Emmert et al., 2010].
© 2016 American Geophysical Union. All rights reserved.
Ionospheric storms caused by geomagnetic activity can be observed using total electron
content (TEC) scintillations based on global navigation satellite systems (GNSSes)
observations, ionosonde observations, and other independent measurements of the
ionospheric plasma [Pi et al., 1997]. The locations of a subset of GNSS stations used in this
research, and a sample TEC map generated from the observed data are shown in Figure 1.
Blagoveshchenskii [2013] and Schunk and Nagy [2009] described a set of variables to define
the state of the ionosphere during storm-time conditions. These variables include season,
local time, solar activity, storm onset time (or time-since-storm-onset-time), storm intensity,
pre-storm state, and QD latitude. Additionally, ionospheric processes have to be considered
along with processes of other regions of the geospace environment such as thermospheric
circulation, neutral and ion composition changes, gravity waves, acoustic waves, chemical
composition, variations in the electric and magnetic fields, and other couplings with the
magnetosphere and neutral atmosphere [Heelis, 1982; Khazanov, 2011]. During such an
ionospheric storm, there can be both positive and negative TEC anomalies (also known as
phases) due to storm effects of different scales. The durations of the positive and negative
phases typically exhibit a clear latitudinal dependence (i.e., at higher latitudes the negative
phase is prolonged) and seasonal dependence (i.e., negative storms are more pronounced in
the winter) [Mendillo, 2006; Mendillo and Klobuchar, 2006]. These phases are apparent in
electron density (N
e
) variations in the F2 layer (NmF2) and the changes in F2 peak height
(hmF2) [Buonsanto, 1999]. In addition to electron density observations (describing the spatial
distribution of the free electrons), ionospheric scintillation measurements can also be carried
out to provide complementary statistics about irregular structures in the ionosphere, which
are often accompanied by rapid signal phase fluctuations. This could be of particular interest
in regions where polar patches are present [Prikryl et al., 2015]. A comparison of such N
e
and
scintillations in the Arctic region is performed in this paper, followed by analyses of the