Comparison of photometer and global MHD determination of the open‐closed field line boundary

Abstract

[1] We compare open-closed field line boundary positions from the BATS-R-US Global MHD model and CANOPUS photometer measurements of red-line emissions. We choose intervals of steady interplanetary and ionospheric conditions in order to adhere to the ''steady-state'' picture that we are trying to address. Nine intervals are chosen that correspond to stable IMF and auroral conditions that can be simulated with the MHD model. We find that on average, the steady-state BATS-R-US MHD model provides an excellent estimate of the open-closed field line boundary proxy as determined by the red-line auroral emissions. Typical errors between the model calculations of the openclosed field line boundary and the observations are within the inherent error in using the red-line emissions.

Quiet time observations of the open‐closed boundary prior to the CIR‐induced storm of 9 August 2008

“…[29] On the basis of previous work [Lanzerotti et al, 1999] and having shown that observations largely agree (∼83%) with output of the BATSRUS global magnetospheric model (previously established to accurately represent the OCB during quiet geomagnetic conditions [Rae et al, 2004]), we conclude that real-time determination of the OCB can be successfully accomplished with reasonable accuracy using an array of fluxgate magnetometers, as was demonstrated herein for the period 1-9 August 2008, using the PENGUIn-AGO array of fluxgate magnetometer instruments. The steady, repeatable features at the four network locations (shown in Figures 4-6) follow the gross features of the OCBpolar cap environment and make it possible to make more detailed studies of this environment.…”

“…Knowledge of only the size of the polar cap inherently contains no site-specific information and thus is not useful in determining how the OCB varies azimuthally for a prescribed set of space weather parameters. Such precise site-specific information is crucial to many ongoing areas of research which include the investigation of reconnection rates at the magnetopause [Lockwood et al, 2005] and in the magnetotail [Milan, 2004], analyzing how the OCB synoptically transforms throughout the substorm cycle, and modeling the magnetospheric system more accurately [Tsyganenko, 1995;Pulkkinen and Tsyganenko, 1996;Rae et al, 2004;Gombosi et al, 2004].…”

“…11 August time period-an interval that was temporally limited for computational reasons yet, as mentioned above, still included a quiet period (7-9 August) and a CIR period (9-11 August). This particular model was chosen because its predictions of the OCB have been shown to be in good agreement with photometer observations of the OCB during quiet, steady conditions [Rae et al, 2004]. The BATSRUS model utilizes the magnetohydrodynamic equations to study a range of plasma phenomena, including the interaction of the solar wind with planetary magnetospheres Toth et al, 2005].…”

Magnetohydrodynamic simulation of an equatorial dipolar paleomagnetosphere

“…The most popular MHD codes have been compared against each other but, most importantly, reasonably well validated against a variety of in situ spacecraft and ground-based measurements [Janhunen et al, 1995;Fedder et al, 1998;Raeder et al, 1998;Winglee and Menietti, 1998;Gombosi et al, 1998;Raeder et al, 2001;Slinker et al, 2001;White et al, 2001;Siscoe et al, 2002;Kabin et al, 2003;Rae et al, 2004;Ohtani and Raeder, 2004;Nakata et al, 2004].…”

The dependence of Pi2 waveforms on periodic velocity enhancements within bursty bulk flows

“…In this study, we were able to estimate the location of the open-closed separatrix via visual identification of the cutoff in red-line auroral emissions using the CANOPUS GILL meridian scanning photometer (not shown; e.g., Blanchard et al, 1995;Rae et al, 2004), and find that this boundary resides close, but equatorward, of the FCHU station. The largest time lag (which characterises the shortest time of flight) between the in-situ BBF flow bursts and the Pi2 observed along the Churchill Line on the ground is at PINA, deep within the closed field line region, rather than occurring at a station that maps to the reconnection site as proposed by Keiling et al (2006).…”