Solar wind-magnetosphereatmosphere coupling: effects of
magnetic storms and substorms
in atmospheric electric field
variations
Kleimenova N., Kozyreva O.,
Michnowski S., Kubicki M,
Institute of the Earth Physics, Russia
Institute of Geophysics, Poland
Atmospheric electricity
The global electric circuit
The global electric circuit is controlled by the global thunderstorm activity.
Thunderstorm activity draws current upward from the ground. The ionosphere
disperses the current globally, and it leaks back to the surface.
The important points:
• 1. Despite being postulated since at least 150 years
[Thomson (Lord Kelvin), 1860], the global electric
circuit is still poorly quantified.
• 2. Solar and magnetosphere activity influences due
to ionosphere electric field disturbances may
significantly control a global electric circuit state.
• 3. The geoelectric circuit links weather and solar
activity. It remains the open question whether this
linkage is passive or involves active coupling.
The aim of our investigations is to study an
atmospheric electricity response to the
magnetic storms and substorms.
•
Our studying was based on the observations of the
vertical electric field (Ez) at two ground-based points:
the middle latitude Swider station as well as at the
polar latitude Hornsund station.
• To avoid meteorological influences we used Ez data,
obtained only under so called “fair weather”
conditions, which request the absence of a rain, snow,
fog, lower clouds, and wind velocity more 6 m/c. We
could find not more than ~ 40-60 full days under “fair
weather” condition in the year (i.e., ~12-15% of the total
observations)
MIDDLE LATITUDES
Coordinates:
obs. Swider (Poland)
Geomagnetic Φ=47.8º, Λ=96.8º
Local magnetic noon at ~10 UT
Ez daily variations under Kp<2
Asia
Africa
Global thunderstorm activity
Magnetic storm effect in the Ez variations
• We have analyzed 14 magnetic storms in 20002004 observed under “fair weather” periods. It
was typical that the main phase of the magnetic
storms was accompanied by intense night-side
magnetic substorms.
• The storm-time Ez anomalies are better
manifested by comparing the recorded data with
Ez daily variations obtained under the quiet
magnetic conditions (at least Kp<2).
Asia
Ez
Ez – Ez(quiet)
Day side
BEL
Night
CMO
SOD
Africa
BEL
CMO
SOD
Results
•
For the first time the magnetic storm effect was found in the
mid-latitude Ez variations.
• Our study showed that during the main phase of a magnetic
storm a strong daytime negative Ez deviations were observed at
middle latitudes simultaneously with magnetic substorm
developing at night side of the auroral zone under any local midlatitude magnetic perturbations.
• The considered Ez deviations could be associated with the
interplanetary electric field enhancement and it deep penetration
into the magnetosphere.
• Another plausible reason could be related to the common
ionosphere conductivity increasing due to substorm energetic
electron precipitation because the high-latitude ionosphere is an
important part of the global atmospheric electric circuit.
Two examples of the Forbush decrease
influence to the Ez changes
Dst
AE
Forbush decrease
averaged Ez level
Forbush Ez level
The strong Ez depletion in the days of Forbush decrease development is seen.
In the polar regions, the interaction of the solar wind and
the Earth's magnetic field causes the two-cell convection
patterns in the polar ionosphere.
Solar influence on the
atmospheric electric field
differs between middle and
polar latitudes.
_
+
The polar cap potential
can produce significant
vertical electric fields (Ez)
at the ground level.
Obs. Hornsund (Spitsbergen)
COORDINATES Φ=74º, Λ=110.5º
HOR
Substorm effects in Ez at polar latitudes (obs. Hornsund)
morning
night
morning
night
74º
64º
Two examples of a negative Ez deviation during the night substorms
and a positive Ez deviation during the morning substorms
Global structure of high latitude plasma convection
during the considered morning substorms at
Scandinavian meridian according to the
SUPERDARN data
Global structure of high latitude plasma
convection during the considered night-time
substorms at Scandinavian meridian according to
the SUPERDARN data
The auroral oval location during the considered
substorm
Ez
X
CONCLUSION
Magnetic storms and substorms, caused by
solar wind and interplanetary magnetic field
disturbances, could influence to the global
electric circuit state via changing of
ionosphere conductivity due to particle
precipitations or via cosmic rays, or via the
direct interplanetary electric field penetration
into magnetosphere, or via the polar cap
convection changes.
Thus, the variations in the atmospheric
electricity both in middle and polar latitudes
represent one of the final stage of the solar
wind-magnetosphere-atmosphere coupling.
THANK YOU FOR ATTENTION!
My coauthors: S. Michnowski, O Kozyreva, M.Kubicki
Magnetic storm initial phase
SC
Ez
Pd
Np
HOR
Vx
B
Bx
B
X
B
By
Bz
SOD
Bz IMF = +36 nT