High-latitude observations of solar wind streams and coronal holes

High-speed streams (HSS) from coronal holes dominate solar wind structure in the absence of coronal mass ejections during solar minimum and the descending branch of solar cycle. Prominent and long-lasting coronal holes produce intense co-rotating interaction regions (CIR) on the leading edge of high-speed plasma streams that cause recurrent ionospheric disturbances and geomagnetic storms. Through solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system they affect the ionosphere and neutral atmosphere at high latitudes, and, at mid to low latitudes, by the transmission of the electric fields [1] and propagation of atmospheric gravity waves from the high-latitude lower thermosphere [2].The high-latitude ionospheric structure, caused by precipitation of energetic particles, strong ionospheric currents and convection, results in changes of the GPS total electron content (TEC) and rapid variations of GPS signal amplitude and phase, called scintillation [3]. The GPS phase scintillation is observed in the ionospheric cusp, polar cap and auroral zone, and is particularly intense during geomagnetic storms, substorms and auroral breakups. Phase scintillation index is computed for a sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy index of phase variation is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of the RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time [4]. Temporal and spatial changes of TEC and phase variations following the arrivals of HSS/CIRs [5] are investigated in the context of ionospheric convection and equivalent ionospheric currents derived from&#160; a ground magnetometer network using the spherical elementary current system method [6,7].The Joule heating and Lorentz forcing in the high-latitude lower thermosphere have long been recognized as sources of internal atmospheric gravity waves (AGWs) [2] that propagate both upward and downward, thus providing vertical coupling between atmospheric layers. In the ionosphere, they are observed as traveling ionospheric disturbances (TIDs) using various techniques, e.g., de-trended GPS TEC maps [8].In this paper we examine the influence on the Earth&#8217;s ionosphere and atmosphere of a long-lasting HSS/CIRs from recurrent coronal holes at the end of solar cycles 23 and 24. The solar wind MIA coupling, as represented by the coupling function [9], was strongly increased during the arrivals of these HSS/CIRs.&#160;[1] Kikuchi, T. and K. K. Hashimoto, Geosci. Lett. , 3:4, 2016.[2] Hocke, K. and K. Schlegel, Ann. Geophys., 14, 917&#8211;940, 1996.[3] Prikryl, P., et al., J. Geophys. Res. Space Physics, 121, 10448&#8211;10465, 2016.[4] Ghoddousi-Fard et al., Advances in Space Research, 52(8), 1397-1405, 2013.[5] Prikryl et al. Earth, Planets and Space, 66:62, 2014.[6] Amm O., and A. Viljanen, Earth Planets Space, 51, 431&#8211;440, 1999.[7] Weygand J.M., et al., J. Geophys. Res., 116, A03305, 2011.[8] Tsugawa T., et al., Geophys. Res. Lett., 34, L22101, 2007.[9] Newell P. T., et al., J. Geophys. Res., 112, A01206, 2007.

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Solar wind from high-latitude coronal holes at solar maximum

Geophysical Research Letters ◽

10.1029/2001gl013940 ◽

2002 ◽

Vol 29 (9) ◽

pp. 28-1-28-4 ◽

Cited By ~ 31

Author(s):

D. J. McComas ◽

H. A. Elliott ◽

R. von Steiger

Keyword(s):

Solar Wind ◽

High Latitude ◽

Solar Maximum ◽

Coronal Holes

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Velocity fluctuations in polar solar wind: a comparison between different solar cycles

Annales Geophysicae ◽

10.5194/angeo-27-877-2009 ◽

2009 ◽

Vol 27 (2) ◽

pp. 877-883 ◽

Cited By ~ 2

Author(s):

B. Bavassano ◽

R. Bruno ◽

R. D'Amicis

Keyword(s):

Solar Wind ◽

Wind Velocity ◽

High Latitude ◽

Coronal Holes ◽

Dimensional Structure ◽

Time Lags ◽

Solar Cycles ◽

Polar Wind ◽

Activity Maximum ◽

Velocity Fluctuations

Abstract. The polar solar wind is a fast, tenuous and steady flow that, with the exception of a relatively short phase around the Sun's activity maximum, fills the high-latitude heliosphere. The polar wind properties have been extensively investigated by Ulysses, the first spacecraft able to perform in-situ measurements in the high-latitude heliosphere. The out-of-ecliptic phases of Ulysses cover about seventeen years. This makes possible to study heliospheric properties at high latitudes in different solar cycles. In the present investigation we focus on hourly- to daily-scale fluctuations of the polar wind velocity. Though the polar wind is a quite uniform flow, fluctuations in its velocity do not appear negligible. A simple way to characterize wind velocity variations is that of performing a multi-scale statistical analysis of the wind velocity differences. Our analysis is based on the computation of velocity differences at different time lags and the evaluation of statistical quantities (mean, standard deviation, skewness, and kurtosis) for the different ensembles. The results clearly show that, though differences exist in the three-dimensional structure of the heliosphere between the investigated solar cycles, the velocity fluctuations in the core of polar coronal holes exhibit essentially unchanged statistical properties.

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Relation of solar wind parameters to high-latitude magnetic pulsations

Kosmìčna nauka ì tehnologìâ ◽

10.15407/knit2006.01.080 ◽

2006 ◽

Vol 12 (1) ◽

pp. 80-84

Author(s):

S.N. Samsonov ◽

◽

I.Ya. Plotnikov ◽

D.Y. Sibeck ◽

Yu. Watermann ◽

...

Keyword(s):

Solar Wind ◽

High Latitude ◽

Magnetic Pulsations ◽

Solar Wind Parameters

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Comparative Analysis of Terrestrial and Satellite Observations of Photospheric Magnetic Field in an Appendix to Simulation of Parameters of Coronal Holes and Solar Wind

Geomagnetism and Aeronomy ◽

10.1134/s0016793220070051 ◽

2020 ◽

Vol 60 (7) ◽

pp. 872-875

Author(s):

I. A. Berezin ◽

A. G. Tlatov

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Comparative Analysis ◽

Coronal Holes ◽

Satellite Observations ◽

Photospheric Magnetic Field

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The influence of solar wind on extratropical cyclones – Part 1: Wilcox effect revisited

Annales Geophysicae ◽

10.5194/angeo-27-1-2009 ◽

2009 ◽

Vol 27 (1) ◽

pp. 1-30 ◽

Cited By ~ 24

Author(s):

P. Prikryl ◽

V. Rušin ◽

M. Rybanský

Keyword(s):

Time Series ◽

Solar Wind ◽

Northern Hemisphere ◽

High Speed ◽

Coronal Holes ◽

Extratropical Cyclones ◽

Sector Boundary ◽

Speed Solar Wind ◽

The Mean ◽

High Speed Solar Wind

Abstract. A sun-weather correlation, namely the link between solar magnetic sector boundary passage (SBP) by the Earth and upper-level tropospheric vorticity area index (VAI), that was found by Wilcox et al. (1974) and shown to be statistically significant by Hines and Halevy (1977) is revisited. A minimum in the VAI one day after SBP followed by an increase a few days later was observed. Using the ECMWF ERA-40 re-analysis dataset for the original period from 1963 to 1973 and extending it to 2002, we have verified what has become known as the "Wilcox effect" for the Northern as well as the Southern Hemisphere winters. The effect persists through years of high and low volcanic aerosol loading except for the Northern Hemisphere at 500 mb, when the VAI minimum is weak during the low aerosol years after 1973, particularly for sector boundaries associated with south-to-north reversals of the interplanetary magnetic field (IMF) BZ component. The "disappearance" of the Wilcox effect was found previously by Tinsley et al. (1994) who suggested that enhanced stratospheric volcanic aerosols and changes in air-earth current density are necessary conditions for the effect. The present results indicate that the Wilcox effect does not require high aerosol loading to be detected. The results are corroborated by a correlation with coronal holes where the fast solar wind originates. Ground-based measurements of the green coronal emission line (Fe XIV, 530.3 nm) are used in the superposed epoch analysis keyed by the times of sector boundary passage to show a one-to-one correspondence between the mean VAI variations and coronal holes. The VAI is modulated by high-speed solar wind streams with a delay of 1–2 days. The Fourier spectra of VAI time series show peaks at periods similar to those found in the solar corona and solar wind time series. In the modulation of VAI by solar wind the IMF BZ seems to control the phase of the Wilcox effect and the depth of the VAI minimum. The mean VAI response to SBP associated with the north-to-south reversal of BZ is leading by up to 2 days the mean VAI response to SBP associated with the south-to-north reversal of BZ. For the latter, less geoeffective events, the VAI minimum deepens (with the above exception of the Northern Hemisphere low-aerosol 500-mb VAI) and the VAI maximum is delayed. The phase shift between the mean VAI responses obtained for these two subsets of SBP events may explain the reduced amplitude of the overall Wilcox effect. In a companion paper, Prikryl et al. (2009) propose a new mechanism to explain the Wilcox effect, namely that solar-wind-generated auroral atmospheric gravity waves (AGWs) influence the growth of extratropical cyclones. It is also observed that severe extratropical storms, explosive cyclogenesis and significant sea level pressure deepenings of extratropical storms tend to occur within a few days of the arrival of high-speed solar wind. These observations are discussed in the context of the proposed AGW mechanism as well as the previously suggested atmospheric electrical current (AEC) model (Tinsley et al., 1994), which requires the presence of stratospheric aerosols for a significant (Wilcox) effect.

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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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Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling

Annales Geophysicae ◽

10.5194/angeo-22-3537-2004 ◽

2004 ◽

Vol 22 (10) ◽

pp. 3537-3560 ◽

Cited By ~ 19

Author(s):

P. E. Sandholt ◽

C. J. Farrugia ◽

W. F. Denig

Keyword(s):

Solar Wind ◽

Local Time ◽

High Latitude ◽

Specific Activity ◽

Moderate Intensity ◽

Auroral Activity ◽

Activity Intensity ◽

Subsolar Point ◽

Field Lines ◽

Ground Magnetic

Abstract. In two case studies we elaborate on spatial and temporal structures of the dayside aurora within 08:00-16:00 magnetic local time (MLT) and discuss the relationship of this structure to solar wind-magnetosphere interconnection topology and the different stages of evolution of open field lines in the Dungey convection cycle. The detailed 2-D auroral morphology is obtained from continuous ground observations at Ny Ålesund (76° magnetic latitude (MLAT)), Svalbard during two days when the interplanetary magnetic field (IMF) is directed southeast (By>0; Bz<0). The auroral activity consists of the successive activations of the following forms: (i) latitudinally separated, sunward moving, arcs/bands of dayside boundary plasma sheet (BPS) origin, in the prenoon (08:00-11:00 MLT) and postnoon (12:00-16:00 MLT) sectors, within 70-75° MLAT, (ii) poleward moving auroral forms (PMAFs) emanating from the pre- and postnoon brightening events, and (iii) a specific activity appearing in the 07:00-10:00 MLT/75-80° MLAT during the prevailing IMF By>0 conditions. The pre- and postnoon activations are separated by a region of strongly attenuated auroral activity/intensity within the 11:00-12:00 MLT sector, often referred to as the midday gap aurora. The latter aurora is attributed to the presence of component reconnection at the subsolar magnetopause where the stagnant magnetosheath flow lead to field-aligned currents (FACs) which are of only moderate intensity. The much more active and intense aurorae in the prenoon (07:00-11:00 MLT) and postnoon (12:00-16:00 MLT) sectors originate in magnetopause reconnection events that are initiated well away from the subsolar point. The high-latitude auroral activity in the prenoon sector (feature iii) is found to be accompanied by a convection channel at the polar cap boundary. The associated ground magnetic deflection (DPY) is a Svalgaard-Mansurov effect. The convection channel is attributed to effective momentum transfer from the solar wind-magnetosphere dynamo in the high-latitude boundary layer (HBL), on the downstream side of the cusp.

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