Interhemispheric observations of the ionospheric signature of tail reconnection during IMF-northward non-substorm intervals

Abstract. This paper presents the first interhemispheric radar observations interpreted as the ionospheric response to tail reconnection during IMF-northward non-substorm intervals. SuperDARN measurements of plasma convection in the nightside ionospheres of both hemispheres, taken on 21–22 February and 26–27 April 2000, show bursts of flow in the midnight sector which are understood to be characteristic of such phenomena. Upstream interplanetary magnetic field data confirm that the field orientation at the dayside magnetopause was northwards, but with a significant IMF By component (negative during the first interval, positive during the second), for many hours prior to the bursts being observed. During the By-negative interval the bursts were directed westwards in the Northern Hemisphere and eastwards in the Southern Hemisphere; during the By-positive interval their directions were reversed. These two asymmetries between the different orientations of IMF By and between the two hemispheres are key to our understanding of the magnetospheric phenomenon responsible for generating the bursts. They provide further evidence in support of the idea that the bursts are a result of reconnection in an asymmetric tail under the prolonged influence of IMF By. Concurrent data from ground magnetometers and geosynchronous satellites confirm that the bursts have no associated substorm characteristics, consistent with previous studies. Keywords. Ionosphere (Plasma convection; Ionospheremagnetosphere interactions) – Magnetospheric Physics (Magnetotail)

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Central polar cap convection response to short duration southward Interplanetary Magnetic Field

Annales Geophysicae ◽

10.1007/s00585-000-0887-z ◽

2000 ◽

Vol 18 (8) ◽

pp. 887-896 ◽

Cited By ~ 10

Author(s):

P. T. Jayachandran ◽

J. W. MacDougall

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Short Duration ◽

Initial Response ◽

Plasma Convection ◽

Polar Cap ◽

Ionosphere Plasma ◽

Rapid Transition ◽

Convection Speed ◽

A Chain

Abstract. Central polar cap convection changes associated with southward turnings of the Interplanetary Magnetic Field (IMF) are studied using a chain of Canadian Advanced Digital Ionosondes (CADI) in the northern polar cap. A study of 32 short duration (~1 h) southward IMF transition events found a three stage response: (1) initial response to a southward transition is near simultaneous for the entire polar cap; (2) the peak of the convection speed (attributed to the maximum merging electric field) propagates poleward from the ionospheric footprint of the merging region; and (3) if the change in IMF is rapid enough, then a step in convection appears to start at the cusp and then propagates antisunward over the polar cap with the velocity of the maximum convection. On the nightside, a substorm onset is observed at about the time when the step increase in convection (associated with the rapid transition of IMF) arrives at the polar cap boundary.Key words: Ionosphere (plasma convection; polar ionosphere) - Magnetospheric physics (solar wind - magnetosphere interaction)

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Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field

Annales Geophysicae ◽

10.5194/angeo-22-4243-2004 ◽

2004 ◽

Vol 22 (12) ◽

pp. 4243-4258 ◽

Cited By ~ 29

Author(s):

G. Chisham ◽

M. P. Freeman ◽

I. J. Coleman ◽

M. Pinnock ◽

M. R. Hairston ◽

...

Keyword(s):

Magnetic Field ◽

Electric Field ◽

Interplanetary Magnetic Field ◽

Line Length ◽

Hf Radar ◽

Plasma Convection ◽

Ionosphere Plasma ◽

Reconnection Region ◽

Field Lines ◽

First Time

Abstract. This study presents, for the first time, detailed spatiotemporal measurements of the reconnection electric field in the Northern Hemisphere ionosphere during an extended interval of northward interplanetary magnetic field. Global convection mapping using the SuperDARN HF radar network provides global estimates of the convection electric field in the northern polar ionosphere. These are combined with measurements of the ionospheric footprint of the reconnection X-line to determine the spatiotemporal variation of the reconnection electric field along the whole X-line. The shape of the spatial variation is stable throughout the interval, although its magnitude does change with time. Consequently, the total reconnection potential along the X-line is temporally variable but its typical magnitude is consistent with the cross-polar cap potential measured by low-altitude satellite overpasses. The reconnection measurements are mapped out from the ionosphere along Tsyganenko model magnetic field lines to determine the most likely reconnection location on the lobe magnetopause. The X-line length on the lobe magnetopause is estimated to be ~6–11 RE in extent, depending on the assumptions made when determining the length of the ionospheric X-line. The reconnection electric field on the lobe magnetopause is estimated to be ~0.2mV/m in the peak reconnection region. Key words. Space plasma physics (Magnetic reconnection) – Magnetospheric physics (Magnetopause, cusp and boundary layers) – Ionosphere (Plasma convection)

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Magnetopause magnetic barrier parameters in dependence on the solar wind magnetic field orientation

Annales Geophysicae ◽

10.1007/s00585-995-0828-y ◽

1995 ◽

Vol 13 (8) ◽

pp. 828-835 ◽

Cited By ~ 9

Author(s):

M. I. Pudovkin ◽

S. A. Zaitseva ◽

B. P. Besser

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Field Strength ◽

Interplanetary Magnetic Field ◽

Opposite Effect ◽

Field Orientation ◽

Magnetic Field Orientation ◽

Dayside Magnetopause ◽

Solar Wind Magnetic Field ◽

Theoretical Predictions

Abstract. Some theories predict the magnetosheath magnetic field strength will decrease and the density increase just outside the dayside magnetopause as the interplanetary magnetic field turns southward. Two studies have recently reported results which confirm these expectations. In contrast, we briefly review our own theoretical predictions which indicate that precisely the opposite effect is expected. We survey new and previously reported magnetosheath observations and demonstrate that they are consistent with the predictions of our model. The conflicting results indicate a need for further theoretical and observational work.

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Large-Scale Magnetic Field Structure at the Earth's Orbit, Its Correlation with Solar Activity and Orientation and Motion of the Solar System in the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900067528 ◽

1980 ◽

Vol 91 ◽

pp. 167-172

Author(s):

G. J. Vassilyeva ◽

M. A. Kuznetsova ◽

L. M. Kotlyar

Keyword(s):

Magnetic Field ◽

Solar Activity ◽

Solar System ◽

Interplanetary Magnetic Field ◽

Field Data ◽

Large Scale ◽

Field Structure ◽

Magnetic Field Data ◽

Large Scale Magnetic Field ◽

The Galaxy

Interplanetary magnetic field data from the different satellites obtained during the period 1963-1973 at 1 A.U. and compiled by J. King have been analysed in heliocentric ecliptic coordinates. The peculiarities of the background interplanetary magnetic field (BIMF) are discussed in relation to the orientation of the solar system in the Galaxy and the variable helioefficiency of the planets. The results of the direct cosmic experiments are evidence of the solar activity being a complex phenomenon of the solar system as a whole.

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Interplanetary magnetic field data and corresponding geomagnetic effects for the storm of October 7, 1962

Journal of Geophysical Research Atmospheres ◽

10.1029/jz072i013p03471 ◽

1967 ◽

Vol 72 (13) ◽

pp. 3471-3482 ◽

Cited By ~ 13

Author(s):

R. Zelwer ◽

P. C. B. Fernando ◽

S. H. Ward

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Field Data ◽

Magnetic Field Data

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An Augmented Iteratively Re-weighted and Refined Least Squares Method for lp Minimization Problem in Inverse Modeling of Potential Field Magnetic Data

Journal of Geological Research ◽

10.30564/jgr.v1i3.1316 ◽

2020 ◽

Vol 1 (3) ◽

Author(s):

Maysam Abedi

Keyword(s):

Magnetic Field ◽

Magnetic Susceptibility ◽

Least Squares ◽

Minimization Problem ◽

Potential Field ◽

Field Data ◽

Least Squares Method ◽

Porphyry Copper ◽

Magnetic Data ◽

Magnetic Field Data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit. The real case study located in Semnan province of Iran consists of an arc-shaped porphyry andesite covered by sedimentary units which may have potential of mineral occurrences, especially porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

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INFLUENCE OF THE INTERPLANETARY MAGNETIC FIELD ORIENTATION ON NORTH-SOUTHERN ASYMMETRY OF ULF WAVE PACKETS IN THE POLAR CAPS

Геофизические исследования ◽

10.21455/gr2019.2-2 ◽

2019 ◽

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Wave Packets ◽

Field Orientation ◽

Magnetic Field Orientation ◽

Ulf Wave ◽

Polar Caps

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Interplanetary magnetic field control of Saturn's polar cusp aurora

Annales Geophysicae ◽

10.5194/angeo-23-1405-2005 ◽

2005 ◽

Vol 23 (4) ◽

pp. 1405-1431 ◽

Cited By ~ 48

Author(s):

E. J. Bunce ◽

S. W. H. Cowley ◽

S. E. Milan

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interplanetary Magnetic Field ◽

Field Line ◽

High Latitude ◽

Closed Field ◽

Vortical Flows ◽

Dayside Magnetopause ◽

Closed Field Line ◽

Lobe Reconnection

Abstract. Dayside UV emissions in Saturn's polar ionosphere have been suggested to be the first observational evidence of the kronian "cusp" (Gérard et al., 2004). The emission has two distinct states. The first is a bright arc-like feature located in the pre-noon sector, and the second is a more diffuse "spot" of aurora which lies poleward of the general location of the main auroral oval, which may be related to different upstream interplanetary magnetic field (IMF) orientations. Here we take up the suggestion that these emissions correspond to the cusp. However, direct precipitation of electrons in the cusp regions is not capable of producing significant UV aurora. We have therefore investigated the possibility that the observed UV emissions are associated with reconnection occurring at the dayside magnetopause, possibly pulsed, akin to flux transfer events seen at the Earth. We devise a conceptual model of pulsed reconnection at the low-latitude dayside magnetopause for the case of northwards IMF which will give rise to pulsed twin-vortical flows in the magnetosphere and ionosphere in the vicinity of the open-closed field-line boundary, and hence to bi-polar field-aligned currents centred in the vortical flows. During intervals of high-latitude lobe reconnection for southward IMF, we also expect to have pulsed twin-vortical flows and corresponding bi-polar field-aligned currents. The vortical flows in this case, however, are displaced poleward of the open-closed field line boundary, and are reversed in sense, such that the field-aligned currents are also reversed. For both cases of northward and southward IMF we have also for the first time included the effects associated with the IMF By effect. We also include the modulation introduced by the structured nature of the solar wind and IMF at Saturn's orbit by developing "slow" and "fast" flow models corresponding to intermediate and high strength IMF respectively. We then consider the conditions under which the plasma populations appropriate to either sub-solar reconnection or high-latitude lobe reconnection can carry the currents indicated. We have estimated the field-aligned voltages required, the resulting precipitating particle energy fluxes, and the consequent auroral output. Overall our model of pulsed reconnection under conditions of northwards and southwards IMF, and for varying orientations of IMF By, is found to produce a range of UV emission intensities and geometries which is in good agreement with the data presented by Gérard et al. (2004). The recent HST-Cassini solar wind campaign provides a unique opportunity to test the theoretical ideas presented here.

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