Statistics of Joule heating in the auroral zone and polar cap using Astrid-2 satellite Poynting flux

Olsson, Annika; Janhunen, P.; Karlsson, Tomas; Ivchenko, Nickolay; Blomberg, Lars G.

doi:10.5194/angeo-22-4133-2004

Cited by 32 publications

(56 citation statements)

References 15 publications

(38 reference statements)

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“…Statistically, the level of the particle precipitation is rather well known (Hardy et al, 1987(Hardy et al, , 1989. There are also several statistical satellite studies of the Joule heating (Foster et al, 1983;Gary et al, 1995;Olsson et al, 2004a) that are in quite good agreement with each other, despite the different types of instrumentation used .…”

Section: Introductionsupporting

confidence: 54%

“…In panels (b-e), dark-blue and reddish bar at R=0.7 − 1 is electron precipitation power per area from the Hardy et al (1987) model for low K p (≤2) and high K p (>2), respectively. In panel (e), blue and red bar at R=1 − 1.3 is DC Poynting vector from Astrid-2 satellite (1000 km altitude) from Olsson et al (2004a) and in panel (a), the corresponding bar shows the orbital coverage of Astrid-2. To compensate for the fact that only the spin-plane components of Polar electric field are used, all measured Polar Poynting vectors are multiplied by 1.5 (see text for motivation).…”

Section: Radial Distancementioning

confidence: 99%

“…To approximately calibrate the Polar statistical result with respect to the missing electric field component, we use a recent work where the low-altitude (1000 km) parallel Poynting vector was studied using Astrid-2 data (Blomberg et al, 2004;Olsson et al, 2004a). The spin plane of Astrid-2 is nominally perpendicular to the EarthSun line, which makes it possible in many cases to accurately resolve the 3-D electric field using the E×B=0 assumption (Ivchenko et al, 2001;Olsson et al, 2004a). We reprocessed the Astrid-2 data set by setting the zonal electric field artificially to zero.…”

Section: Instrumentationmentioning

confidence: 99%

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Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

et al. 2005

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Abstract. We study the wave-related (AC) and static (DC) parallel Poynting vector (Poynting energy flux) as a function of altitude in auroral field lines using Polar EFI and MFE data. The study is statistical and contains 5 years of data in the altitude range 5000-30 000 km. We verify the low altitude part of the results by comparison with earlier Astrid-2 EMMA Poynting vector statistics at 1000 km altitude. The EMMA data are also used to statistically compensate the Polar results for the missing zonal electric field component. We compare the Poynting vector with previous statistical DMSP satellite data concerning the electron precipitation power. We find that the AC Poynting vector (Alfvén-wave related Poynting vector) is statistically not sufficient to power auroral electron precipitation, although it may, for K p >2, power 25-50% of it. The statistical AC Poynting vector also has a stepwise transition at R=4 R E , so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfvén waves being in Landau resonance with electrons, so that wave-induced electron acceleration takes place at this altitude range, which was earlier named the Alfvén Resonosphere (ARS). The DC Poynting vector is ∼3 times larger than electron precipitation and corresponds mainly to ionospheric Joule heating. In the morning sector (02:00-06:00 MLT) we find that the DC Poynting vector has a nontrivial altitude profile such that it decreases by a factor of ∼2 when moving upward from 3 to 4 R E radial distance. In other nightside MLT sectors the altitude profile is more uniform. The morning sector nontrivial altitude profile may be due to divergence of the perpendicular Poynting vector field at R=3−4 R E .

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Section: Introductionsupporting

confidence: 54%

Section: Radial Distancementioning

confidence: 99%

Section: Instrumentationmentioning

confidence: 99%

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Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

et al. 2005

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“…Schlegel (1988) found that conductances are higher in the winter than in summer; both studies were for the Northern Hemisphere. Olsson et al (2004) obtained different formulas for global Joule heating estimates during summer, equinox and winter. Clearly a larger database with simultaneous high spatial and temporal resolution electric field and conductance measurements would be needed in order to discern all the effects discussed above affecting the Joule heating rate.…”

Section: Discussionmentioning

confidence: 99%

“…Olsson et al (2004) have presented fitted global Joule heating formulas under given solar illumination conditions as a function of K p , AE, the Akasofu epsilon parameter and the solar wind kinetic energy flux.…”

Section: Introductionmentioning

confidence: 99%

Statistical properties of Joule heating rate, electric field and conductances at high latitudes

Aikio

Selkälä

2009

Ann. Geophys.

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Abstract. Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat) from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox) and from similar sunspot conditions (about 1.5 years before the sunspot minimum) providing an excellent set of data to study the MLT and K p dependence of parameters with high temporal and spatial resolution.All the parameters show a clear MLT variation, which is different for low and high K p conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03-05 MLT for K p ≥ 3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity.An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (K p < 3 and K p ≥ 3). In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcsCorrespondence to: A. T. Aikio (anita.aikio@oulu.fi) as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004). In addition, a part of the anticorrelation may come from polarization effects inside highconductance regions, e.g. auroral arcs. These observations confirm the speculated effect of small scale electrodynamics, which is not included in most of the global modeling efforts of Joule heating rate.

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Empirical model of Poynting flux derived from FAST data and a cusp signature

et al. 2014

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[1] Empirical models of the Poynting flux and particle kinetic energy flux, associated with auroral processes, have been constructed using data from the FAST satellite and are available online. The models output flux maps as a function of several geophysical parameters: (1) clock angle of the interplanetary magnetic field (IMF), (2) magnitude of the IMF in the GSM y-z plane, (3) solar wind speed, (4) solar wind number density, (5) magnetic dipole tilt angle, and (6) the AL index (optional for Poynting flux). The choice of parameters is motivated by the Weimer potential model. Because the Poynting flux distribution has a heavy tail, care must be taken in applying the model to events that may be uncommon, and the model output includes a measure of quality based on the density of FAST orbits in the parameter space. The models are constructed by fitting the data to a sum of empirical orthogonal functions (EOFs), with coefficients modeled by quadratic equations in the geophysical parameters. The EOFs are constructed from the same data set using singular value decomposition, along with a smoothing/interpolation algorithm that minimizes curvature and incorporates uncertainty. Potential applications include specification of the auroral energy input for general circulation models. Basic findings from the model include verification of the importance of the auroral electrojets as features of auroral Poynting flux deposition and identification of the cusp as a third important feature. The cusp makes an important contribution to the overall energy budget when the IMF is north of˙90 ı .

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Statistics of Joule heating in the auroral zone and polar cap using Astrid-2 satellite Poynting flux

Cited by 32 publications

References 15 publications

Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

Statistical properties of Joule heating rate, electric field and conductances at high latitudes

Empirical model of Poynting flux derived from FAST data and a cusp signature

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