scholarly journals Magnetopause reconnection rate estimates for Jupiter's magnetosphere based on interplanetary measurements at ~5AU

2006 ◽  
Vol 24 (1) ◽  
pp. 393-406 ◽  
Author(s):  
J. D. Nichols ◽  
S. W. H. Cowley ◽  
D. J. McComas
Keyword(s):  
Solar Cycle ◽  
High Latitude ◽  
Solar Rotation ◽  
Dynamic Pressure ◽  
Tail Length ◽  
Potential Drop ◽  
Reconnection Rate ◽  
Low Latitude ◽  
Open Flux ◽  
Magnetopause Reconnection

Abstract. We make the first quantitative estimates of the magnetopause reconnection rate at Jupiter using extended in situ data sets, building on simple order of magnitude estimates made some thirty years ago by Brice and Ionannidis (1970) and Kennel and Coroniti (1975, 1977). The jovian low-latitude magnetopause (open flux production) reconnection voltage is estimated using the Jackman et al. (2004) algorithm, validated at Earth, previously applied to Saturn, and here adapted to Jupiter. The high-latitude (lobe) magnetopause reconnection voltage is similarly calculated using the related Gérard et al. (2005) algorithm, also previously used for Saturn. We employ data from the Ulysses spacecraft obtained during periods when it was located near 5AU and within 5° of the ecliptic plane (January to June 1992, January to August 1998, and April to October 2004), along with data from the Cassini spacecraft obtained during the Jupiter flyby in 2000/2001. We include the effect of magnetospheric compression through dynamic pressure modulation, and also examine the effect of variations in the direction of Jupiter's magnetic axis throughout the jovian day and year. The intervals of data considered represent different phases in the solar cycle, such that we are also able to examine solar cycle dependency. The overall average low-latitude reconnection voltage is estimated to be ~230 kV, such that the average amount of open flux created over one solar rotation is ~500 GWb. We thus estimate the average time to replenish Jupiter's magnetotail, which contains ~300-500 GWb of open flux, to be ~15-25 days, corresponding to a tail length of ~3.8-6.5 AU. The average high-latitude reconnection voltage is estimated to be ~130 kV, associated with lobe "stirring". Within these averages, however, the estimated voltages undergo considerable variation. Generally, the low-latitude reconnection voltage exhibits a "background" of ~100 kV that is punctuated by one or two significant enhancement events during each solar rotation, in which the voltage is elevated to ~1-3 MV. The high-latitude voltages are estimated to be about a half of these values. We note that the peak values of order a few MV are comparable to the potential drop due to sub-corotating plasma flows in the equatorial magnetosphere between ~20 RJ and the magnetopause, such that during these periods magnetopause reconnection may have a significant effect on the otherwise rotationally dominated magnetosphere. Despite such variations during each solar rotation, however, the total amount of open flux produced during each solar rotation varies typically by less than ~30% on either side of the overall average for that epoch. The averages over individual data epochs vary over the solar cycle from ~600 GWb per solar rotation at solar maximum to ~400 GWb at solar minimum. In addition we show that the IMF sector with positive clock angle is favoured for reconnection when the jovian spin axis clock angle is also positive, and vice versa, although this effect represents a first order correction to the voltage, which is primarily modulated by IMF strength and direction.

Solar Open Magnetic Flux Migration Pattern over Solar Cycles

2019 ◽  
Vol 15 (S354) ◽  
pp. 157-159
Author(s):  
Chia-Hsien Lin ◽  
Guan-Han Huang ◽  
Lou-Chuang Lee
Keyword(s):  
Solar Cycle ◽  
Magnetic Flux ◽  
Solar Observatory ◽  
Migration Pattern ◽  
Polar Regions ◽  
Solar Cycles ◽  
Low Latitude ◽  
Solar Cycle Variation ◽  
Open Magnetic Flux ◽  
Open Flux

AbstractThe objective of this study is to investigate the solar-cycle variation of the areas of solar open magnetic flux regions at different latitudes. The data used in this study are the radial-field synoptic maps from Wilcox Solar Observatory from May 1970 to December 2014, which covers 3.5 solar cycles. Our results reveal a pole-to-pole trans-equatorial migration pattern for both inward and outward open magnetic fluxes. The pattern consists of the open flux regions migrating across the equator, the regions generated at low latitude and migrating poleward, and the regions locally generated at polar regions. The results also indicate the destruction of open flux regions during the migration from pole to equator, and at low latitude regions. The results have been published in Scientific Reports (Huang et al.2017)

scholarly journals Pulsed flows observed during an interval of prolonged northward IMF

2005 ◽  
Vol 23 (4) ◽  
pp. 1207-1225 ◽  
Author(s):  
G. Provan ◽  
M. Lester ◽  
A. Grocott ◽  
S. W. H. Cowley
Keyword(s):  
Northern Hemisphere ◽  
High Latitude ◽  
Low Latitude ◽  
Radar Backscatter ◽  
Flux Transfer Events ◽  
Equatorward Boundary ◽  
Dayside Magnetopause ◽  
Open Flux ◽  
Lobe Reconnection ◽  
The Imf

Abstract. On the 22 December 2002 the interplanetary magnetic field (IMF) was directed northwards for more than 12h. The Northern and Southern Hemisphere SuperDARN radars were used to study global high-latitude convection during this interval, complemented by data from the ACE and DMSP F13 spacecraft. The relative magnitudes of the IMF By and Bz components varied during this period. When the magnitude of the By component was comparable with or dominated the Bz component, signatures of simultaneous low-latitude and lobe reconnection were observed. Specifically two "standard" merging cells were observed in both hemispheres. In the Northern Hemisphere a high-latitude lobe cell was observed within the dusk merging cell, and there was also evidence of a narrow viscous cell located equatorward of this lobe cell. We observed the ionospheric signatures of flux transfer events (FTEs) in both the Northern and Southern Hemispheres, occurring with a periodicity of ~15min. In the Northern Hemisphere the FTEs were associated with a stepwise equatorward progression of the equatorward boundary of radar backscatter on the dayside. When the IMF Bz component was predominantly greater than the IMF By component, we observed a four-cell convection pattern in the Northern Hemisphere, with pulses of reverse reconnection and an associated stepwise poleward retraction of the equatorward boundary of radar backscatter occurring every ~25min. These observations are consistent with pulsed lobe reconnection occurring in both hemispheres, closing open flux and adding closed flux to the dayside magnetopause. So, during this northward IMF interval the location of the sites of reconnection between the IMF and the Earth's magnetosphere, and thus the form of reconnection process, varied with changing IMF conditions. However, the reconnection remained pulsed, with lobe-only reconnection having a significantly longer periodicity compared with simultaneous lobe and low-latitude reconnection.

scholarly journals The Large-scale Magnetic Field in the Global Solar Cycle: Observational Aspects

1991 ◽  
Vol 130 ◽  
pp. 213-217
Author(s):  
V.I. Makarov ◽  
K.R. Sivaraman
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
High Latitude ◽  
Weak Magnetic Field ◽  
Large Scale ◽  
Meridional Flow ◽  
The Sun ◽  
Low Latitude ◽  
Large Scale Magnetic Field ◽  
Global Cycle

Abstract The global solar cycle is considered as an interaction of 3 types of activity: at low-latitude (sunspots), at high-latitude (polar faculae) and the weak magnetic field. The properties of single and 3-fold reversals of the polar magnetic field are considered. The variation spectrum of the large-scale magnetic field of the Sun is analyzed in the range of 1–30 nHz. A dependence between the rate of a poleward meridional flow and phase of the global cycle is discussed.

Properties of Coronal Holes in Solar Cycle 21-23 using McIntosh archive

2018 ◽  
Vol 13 (S340) ◽  
pp. 187-188
Author(s):  
Rakesh Mazumder ◽  
Prantika Bhowmik ◽  
Dibyendu Nandy
Keyword(s):  
Spatial Distribution ◽  
Solar Cycle ◽  
Magnetic Flux ◽  
Coronal Hole ◽  
High Latitude ◽  
Sharp Increase ◽  
Coronal Holes ◽  
Hole Area ◽  
Low Latitudes ◽  
Open Flux

AbstractWe study the properties of coronal holes during solar cycle 21-23 from the McIntosh archive. In the spatial distribution of coronal hole area we find that there is a sharp increase in coronal hole area at high latitude in agreement with expected open flux configuration there. In overall spatiotemporal distribution of coronal hole centroids, we find the dominance of high latitude coronal holes except for the maximum of the solar cycle, when coronal holes mostly appear in low latitudes. This is in agreement with the expected solar cycle evolution of surface magnetic flux.

scholarly journals Motion of the dayside polar cap boundary during substorm cycles: I. Observations of pulses in the magnetopause reconnection rate

2005 ◽  
Vol 23 (11) ◽  
pp. 3495-3511 ◽  
Author(s):  
M. Lockwood ◽  
J. Moen ◽  
A. P. van Eyken ◽  
J. A. Davies ◽  
K. Oksavik ◽  
...  
Keyword(s):  
Field Line ◽  
Rate Variation ◽  
Closed Field ◽  
Reconnection Rate ◽  
Vhf Radar ◽  
Closed Field Line ◽  
Using Data ◽  
Open Flux ◽  
Magnetopause Reconnection ◽  
The Imf

Abstract. Using data from the EISCAT (European Incoherent Scatter) VHF radar and DMSP (Defense Meteorological Satellite Program) spacecraft passes, we study the motion of the dayside open-closed field line boundary during two substorm cycles. The satellite data show that the motions of ion and electron temperature boundaries in EISCAT data, as reported by Moen et al. (2004), are not localised around the radar; rather, they reflect motions of the open-closed field line boundary at all MLT throughout the dayside auroral ionosphere. The boundary is shown to erode equatorward when the IMF points southward, consistent with the effect of magnetopause reconnection. During the substorm expansion and recovery phases, the dayside boundary returns poleward, whether the IMF points northward or southward. However, the poleward retreat was much faster during the substorm for which the IMF had returned to northward than for the substorm for which the IMF remained southward - even though the former substorm is much the weaker of the two. These poleward retreats are consistent with the destruction of open flux at the tail current sheet. Application of a new analysis of the peak ion energies at the equatorward edge of the cleft/cusp/mantle dispersion seen by the DMSP satellites identifies the dayside reconnection merging gap to extend in MLT from about 9.5 to 15.5 h for most of the interval. Analysis of the boundary motion, and of the convection velocities seen near the boundary by EISCAT, allows calculation of the reconnection rate (mapped down to the ionosphere) from the flow component normal to the boundary in its own rest frame. This reconnection rate is not, in general, significantly different from zero before 06:45 UT (MLT<9.5 h) - indicating that the X line footprint expands over the EISCAT field-of-view to earlier MLT only occasionally and briefly. Between 06:45 UT and 12:45 UT (9.5<MLT<15.5 h) reconnection is continuously observed by EISCAT, confirming the (large) MLT extent of the reconnection footprint deduced from the DMSP passes. As well as direct control by the IMF on longer timescales, the derived reconnection rate variation shows considerable pulsing on timescales of 2-20 min during periods of steady southward IMF.

scholarly journals Simultaneous observations of fluctuating cusp aurora and low-latitude magnetopause reconnection

2007 ◽  
Vol 112 (A11) ◽  
pp. n/a-n/a ◽  
Author(s):  
S. A. Fuselier ◽  
S. M. Petrinec ◽  
K. J. Trattner ◽  
M. Fujimoto ◽  
H. Hasegawa
Keyword(s):  
Low Latitude ◽  
Magnetopause Reconnection

scholarly journals Distributions of Arctic and Northwest Atlantic killer whales inferred from oxygen isotopes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cory J. D. Matthews ◽  
Fred J. Longstaffe ◽  
Jack W. Lawson ◽  
Steven H. Ferguson
Keyword(s):  
Oxygen Isotopes ◽  
North Atlantic ◽  
High Latitude ◽  
Newfoundland And Labrador ◽  
Killer Whales ◽  
Low Latitude ◽  
Northwest Atlantic ◽  
Oxygen And Carbon Isotope ◽  
Stable Oxygen ◽  
Morphological Differences

AbstractKiller whales (Orcinus orca) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species’ distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δ18OP) and structural carbonate (δ18OSC, δ13CSC) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δ18O of marine water (δ18Omarine) at location of origin was estimated from dentine δ18OPvalues, and then compared with predicted isoscape values to assign individual distributions. Dentine δ18OPvalues were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δ18OPand estimated δ18Omarinevalues consistent with18O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δ18O values occurs. Several individuals, however, had relatively high values that reflected origins in18O-enriched, low-latitude waters below this boundary. Within-tooth δ18OSCranges on the order of 1–2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.

Sign in / Sign up

Export Citation Format

Share Document