scholarly journals The magnetosphere under weak solar wind forcing

2007 ◽  
Vol 25 (1) ◽  
pp. 191-205 ◽  
Author(s):  
C. J. Farrugia ◽  
A. Grocott ◽  
P. E. Sandholt ◽  
S. W. H. Cowley ◽  
Y. Miyoshi ◽  
...  
Keyword(s):  
Solar Wind ◽  
Strong Shock ◽  
Polar Cap ◽  
Geomagnetic Disturbances ◽  
Low Latitude ◽  
Moderate Amount ◽  
Storm Activity ◽  
Type Interaction ◽  
Open Flux ◽  
Global Indicators

Abstract. The Earth's magnetosphere was very strongly disturbed during the passage of the strong shock and the following interacting ejecta on 21–25 October 2001. These disturbances included two intense storms (Dst*≈−250 and −180 nT, respectively). The cessation of this activity at the start of 24 October ushered in a peculiar state of the magnetosphere which lasted for about 28 h and which we discuss in this paper. The interplanetary field was dominated by the sunward component [B=(4.29±0.77, −0.30±0.71, 0.49±0.45) nT]. We analyze global indicators of geomagnetic disturbances, polar cap precipitation, ground magnetometer records, and ionospheric convection as obtained from SuperDARN radars. The state of the magnetosphere is characterized by the following features: (i) generally weak and patchy (in time) low-latitude dayside reconnection or reconnection poleward of the cusps; (ii) absence of substorms; (iii) a monotonic recovery from the previous storm activity (Dst corrected for magnetopause currents decreasing from ~−65 to ~−35 nT), giving an unforced decreased of ~1.1 nT/h; (iv) the probable absence of viscous-type interaction originating from the Kelvin-Helmholtz (KH) instability; (v) a cross-polar cap potential of just 20–30 kV; (vi) a persistent, polar cap region containing (vii) very weak, and sometimes absent, electron precipitation and no systematic inter-hemisphere asymmetry. Whereas we therefore infer the presence of a moderate amount of open flux, the convection is generally weak and patchy, which we ascribe to the lack of solar wind driver. This magnetospheric state approaches that predicted by Cowley and Lockwood (1992) but has never yet been observed.

scholarly journals The Polar Cap (PC) index combination, PCC: relations to solar wind properties and global magnetic disturbances

2020 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Solar Wind ◽  
Energy Input ◽  
Source Function ◽  
Ring Current ◽  
Mean Deviation ◽  
Polar Cap ◽  
Geomagnetic Disturbances ◽  
The Real ◽  
Dst Index ◽  
Saturation Effects

The non-negative Polar Cap PCC index built from PCN (North) and PCS (South) correlates considerably better with the solar wind merging electric field and is more representative for the total energy input from the solar wind to the magnetosphere and for the development of geomagnetic disturbances than either of the hemispheric indices. The present work shows that the ring current index, Dst, to a high degree of accuracy can be derived from a source function built on the PCC indices. The integration of the PCC-based source function throughout the interval from 1992 to 2018 without attachment to the real Dst indices based on low latitude magnetic observations has generated equivalent Dst values that correlate very well (R=0.86) with the real Dst index values, which are represented with a mean deviation less than 1 nT and an overall rms deviation less than 13 nT. The precise correlation between the real and equivalent Dst values have been used to correct the PCC indices for saturation effects at high intensity disturbance conditions where the Dst index may take values beyond -100 nT. The relations between PCC and the ring current indices, Dst and ASY-H have been used, in addition, to derive the precise timing between polar cap convection processes reflected in the polar cap indices and the formation of the partial and total ring current systems. Building the ring current is considered to represent the energy input from the solar wind, which also powers auroral disturbance processes such as substorms and upper atmosphere heating. Thus, the PCC indices measuring accurately the energy input from the solar wind are powerful tools for space weather monitoring and for solar-terrestrial research.

scholarly journals Substorm onset latitude and the steadiness of magnetospheric convection

2020 ◽  
Author(s):  
Steve Milan ◽  
Jenny Carter ◽  
Maria-Theresia Walach ◽  
Harneet Sangha ◽  
Brian Anderson
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Substorm Onset ◽  
Polar Cap ◽  
Flux Transport ◽  
Low Latitude ◽  
Magnetospheric Convection ◽  
Terrestrial System ◽  
Bulge Region

<p>We study the role of substorms and steady magnetospheric convection (SMC) in magnetic flux transport in the magnetosphere, using observations of field-aligned currents (FACs) by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE).  We identify two classes of substorm, with onsets above and below 65<sup>o</sup> magnetic latitude, which display different nightside FAC morphologies.  We show that the low-latitude onsets develop a poleward-expanding auroral bulge, and identify these as substorms that manifest ionospheric convection-braking in the auroral bulge region.  We show that the high-latitude substorms, which do not experience braking, can evolve into SMC events if the interplanetary magnetic field (IMF) remains southwards for a prolonged period following onset.  Our results provide a new explanation for the differing modes of response of the terrestrial system to solar wind-magnetosphere-ionosphere coupling, as understood in the context of the expanding/contracting polar cap paradigm, by invoking friction between the ionosphere and atmosphere.</p>

The Open Polar Cap of Rotating Magnetospheres

2021 ◽  
Author(s):  
Binzheng Zhang
Keyword(s):  
Solar Wind ◽  
Numerical Experiments ◽  
Polar Cap ◽  
The Earth ◽  
Planetary Rotation ◽  
Cycle Plays ◽  
Terrestrial Magnetosphere ◽  
Open Flux ◽  
Convection Dominated ◽  
Direct Applicability

<p>The classic Dungey cycle plays an essential role in understanding the dynamics of the terrestrial magnetosphere. However, its direct applicability to planetary magnetospheres such as Jupiter is limited, especially when the planetary rotation is much faster than the Earth. We use a series of numerical experiments to show the transition of the terrestrial magnetosphere from a classic Dungey cycle, convection-dominated system to rotation-dominated configurations. The numerical experiments use the Earth's magnetosphere-ionosphere system as a testbed, with modified rotation speed to increase the influence of planetary rotation over solar wind driving, characterized by the ratio between the solar wind merging potential and the polar cap rotation potential. Results show that when the rotation potential of the polar magnetosphere becomes comparable to the merging potential of the solar wind, the classic Dungey cycle is modified by azimuthal transport of magnetic flux, resulting in a more closed polar magnetosphere with a crescent-shaped open flux region in the ionosphere. These numerical experiments provide a theoretical framework for understanding the fundamentals of magnetospheric physics, which is potentially applicable to the Saturn, Jupiter, and exo-planetary systems.</p>

scholarly journals Causality and Information Transfer Between the Solar Wind and the Magnetosphere–Ionosphere System

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 390
Author(s):  
Pouya Manshour ◽  
Georgios Balasis ◽  
Giuseppe Consolini ◽  
Constantinos Papadimitriou ◽  
Milan Paluš
Keyword(s):  
Solar Wind ◽  
Information Transfer ◽  
Linear Time ◽  
Vertical Component ◽  
Causal Link ◽  
Theoretic Approach ◽  
Geomagnetic Disturbances ◽  
Magnetospheric Substorms ◽  
Solar Wind Parameters ◽  
Information Theoretic Approach

An information-theoretic approach for detecting causality and information transfer is used to identify interactions of solar activity and interplanetary medium conditions with the Earth’s magnetosphere–ionosphere systems. A causal information transfer from the solar wind parameters to geomagnetic indices is detected. The vertical component of the interplanetary magnetic field (Bz) influences the auroral electrojet (AE) index with an information transfer delay of 10 min and the geomagnetic disturbances at mid-latitudes measured by the symmetric field in the H component (SYM-H) index with a delay of about 30 min. Using a properly conditioned causality measure, no causal link between AE and SYM-H, or between magnetospheric substorms and magnetic storms can be detected. The observed causal relations can be described as linear time-delayed information transfer.

scholarly journals The story of plumes: the development of a new conceptual framework for understanding magnetosphere and ionosphere coupling

2016 ◽  
Vol 34 (12) ◽  
pp. 1243-1253 ◽  
Author(s):  
Mark B. Moldwin ◽  
Shasha Zou ◽  
Tom Heine
Keyword(s):  
Conceptual Framework ◽  
Ionospheric Plasma ◽  
Short Review ◽  
Auroral Zone ◽  
Causal Chain ◽  
Elevated Plasma ◽  
Polar Cap ◽  
Paper Briefly ◽  
Low Latitude ◽  
F Region

Abstract. The name “plume” has been given to a variety of plasma structures in the Earth's magnetosphere and ionosphere. Some plumes (such as the plasmasphere plume) represent elevated plasma density, while other plumes (such as the equatorial F region plume) represent low-density regions. Despite these differences these structures are either directly related or connected in the causal chain of plasma redistribution throughout the system. This short review defines how plumes appear in different measurements in different regions and describes how plumes can be used to understand magnetosphere–ionosphere coupling. The story of the plume family helps describe the emerging conceptual framework of the flow of high-density–low-latitude ionospheric plasma into the magnetosphere and clearly shows that strong two-way coupling between ionospheric and magnetospheric dynamics occurs not only in the high-latitude auroral zone and polar cap but also through the plasmasphere. The paper briefly reviews, highlights and synthesizes previous studies that have contributed to this new understanding.

scholarly journals Aurora and open magnetic flux during isolated substorms, sawteeth, and SMC events

2007 ◽  
Vol 25 (8) ◽  
pp. 1865-1876 ◽  
Author(s):  
A. D. DeJong ◽  
X. Cai ◽  
R. C. Clauer ◽  
J. F. Spann
Keyword(s):  
Magnetic Flux ◽  
Temporal Variations ◽  
Auroral Oval ◽  
Polar Cap ◽  
Expansion Phase ◽  
Magnetospheric Convection ◽  
Open Magnetic Flux ◽  
Open Flux ◽  
The Individual

Abstract. Using Polar UVI LBHl and IMAGE FUV WIC data, we have compared the auroral signatures and polar cap open flux for isolated substorms, sawteeth oscillations, and steady magnetospheric convection (SMC) events. First, a case study of each event type is performed, comparing auroral signatures and open magnetic fluxes to one another. The latitude location of the auroral oval is similar during isolated substorms and SMC events. The auroral intensity during SMC events is similar to that observed during the expansion phase of an isolated substorm. Examination of an individual sawtooth shows that the auroral intensity is much greater than the SMC or isolated substorm events and the auroral oval is displaced equatorward making a larger polar cap. The temporal variations observed during the individual sawtooth are similar to that observed during the isolated substorm, and while the change in polar cap flux measured during the sawtooth is larger, the percent change in flux is similar to that measured during the isolated substorm. These results are confirmed by a statistical analysis of events within these three classes. The results show that the auroral oval measured during individual sawteeth contains a polar cap with, on average, 150% more magnetic flux than the oval measured during isolated substorms or during SMC events. However, both isolated substorms and sawteeth show a 30% decrease in polar cap magnetic flux during the dipolarization (expansion) phase.

scholarly journals Spectral characteristics of Atlantic seasonal storm frequency

MAUSAM ◽  
2021 ◽  
Vol 57 (4) ◽  
pp. 597-608
Author(s):  
R. P. KANE
Keyword(s):  
Time Series ◽  
Maximum Entropy Method ◽  
Southern Oscillation ◽  
Spectral Characteristics ◽  
Entropy Method ◽  
Sea Surface ◽  
Low Latitude ◽  
Storm Activity ◽  
Oscillation Phenomenon ◽  
Storm Frequency

lkj & o"kZ 1900&2000 dh vof/k esa vVykafVd egklkxj dh rwQkuh xfrfof/k ¼ftUgas rwQku] izpaM rwQku] vkfn uke fn, x, gaS½ ds fofHkUu lwpdkadksa ds dky Jsf.k;ksa dk vuqØe fo’ys"k.k ,e-b-,e-¼vf/kdre ,uVªkWih fof/k½ }kjk rFkk mldh vkofrZrk ds vk;ke ,e- vkj- ,- ¼cgqq lekJ;.k fo’ys"k.k½ }kjk izkIr fd, x, gaSA fiNys dqN o"kksZa ds vkadM+ksa ¼o"kZ 1950 ls vkxss½ ds vuqlkj budh egRoiw.kZ vkofrZrk,¡ n’kd lfgr( f}okf"kZd dYi] f=okf"kZd dYi {ks=ksa rFkk buls mPp {ks=ksa esa Hkh jghA 2-40 o"kkasZ esa 50 feyhckj ds fuEu v{kka’k {ks=h; iou vkSj 2-40 ,oa 2-85 o"kkasZ ds b- ,u- ,l- vks- ¼,y uhuks/nf{k.kh nksyu½ ?kVuk ds ln`’k f}o"khZ dYi nksyu {ks= esa ¼3&4 o"kkasZ½ rwQku lwpdkad 2-40 rFkk 2-85 o"kksZa ds djhc pje ij jgsA mPp vkofrZrk okys {ks=ksa esa rwQku lwpdkad 4-5&5-5-] 8&9] 11&12 rFkk 14&15 o"kkasZ esa pje ij jgs tcfd b- ,u- ,l- vks- 7-4 ,oa 12&14 o"kksZa esa pje ij jgsA cgq n’kdh; Js.kh esa 28&34]40]50&53]61&63]~70 ,oa ~80 o"kksZa esa ¼ijUrq fHkUu lwpdkadksa ds fy, fHkUu&fHkUu½ rwQku pje ij jgs tks LFky ,oa leqnzh lrg ds rkiekuksa ds leku pje ekuksa ds vuq:Ik jgsA dqy lwpdkadksa esa 90 o"kkZsa esa yxHkx 50 izfr’kr dh m/oZ izo`fr jghA     The time series of the various indices of Atlantic storm activity (number of named storms, hurricanes, etc.) for 1900-2000 were subjected to spectral analysis by MEM (Maximum Entropy Method) and amplitudes of the periodicities were obtained by MRA (Multiple Regression Analysis).  For recent data (1950 onwards), significant periodicities were in the quasi-biennial, quasi-triennial regions and also in higher regions, including decadal. In the QBO region (2-3 years), storm indices had peaks near 2.40 and 2.85 years, similar to 2.40 years of 50 hPa low latitude zonal wind and 2.40 and 2.85 years of ENSO (El Niño/Southern Oscillation) phenomenon. In the QTO region (3-4 years), storm indices and ENSO had common peaks near 3.5 years. In higher periodicity regions, storm indices had peaks at 4.5-5.5, 8-9, 11-12 and 14-15 years, while ENSO had peaks at 7.4 and 12-14 years. In the multi-decadal range, storm peaks were at 28-34, 40, 50-53, 61-63, ~70 and ~80 years (but different for different indices), which matched with similar peaks in land and sea surface temperatures. Some indices had large uptrends, ~50% in 90 years.

Sign in / Sign up

Export Citation Format

Share Document