scholarly journals Global Magnetohydrodynamic Simulations: Performance Quantification of Magnetopause Distances and Convection Potential Predictions

2021 ◽  
Vol 8 ◽  
Author(s):  
Agnit Mukhopadhyay ◽  
Xianzhe Jia ◽  
Daniel T. Welling ◽  
Michael W. Liemohn
Keyword(s):  
Polar Cap ◽  
Weather Patterns ◽  
Performance Metric ◽  
Radar Network ◽  
Metric Analysis ◽  
Ionospheric Electrodynamics ◽  
Model Predictions ◽  
Cross Polar Cap Potential ◽  
Magnetohydrodynamic Simulations ◽  
Almost All

The performance of three global magnetohydrodynamic (MHD) models in estimating the Earth's magnetopause location and ionospheric cross polar cap potential (CPCP) have been presented. Using the Community Coordinated Modeling Center's Run-on-Request system and extensive database on results of various magnetospheric scenarios simulated for a variety of solar weather patterns, the aforementioned model predictions have been compared with magnetopause standoff distance estimations obtained from six empirical models, and with cross polar cap potential estimations obtained from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) Model and the Super Dual Auroral Radar Network (SuperDARN) observations. We have considered a range of events spanning different space weather activity to analyze the performance of these models. Using a fit performance metric analysis for each event, the models' reproducibility of magnetopause standoff distances and CPCP against empirically-predicted observations were quantified, and salient features that govern the performance characteristics of the modeled magnetospheric and ionospheric quantities were identified. Results indicate mixed outcomes for different models during different events, with almost all models underperforming during the extreme-most events. The quantification also indicates a tendency to underpredict magnetopause distances in the absence of an inner magnetospheric model, and an inclination toward over predicting CPCP values under general conditions.

scholarly journals On the SuperDARN cross polar cap potential saturation effect

2009 ◽  
Vol 27 (10) ◽  
pp. 3755-3764 ◽  
Author(s):  
A. V. Koustov ◽  
G. Ya. Khachikjan ◽  
R. A. Makarevich ◽  
C. Bryant
Keyword(s):  
Electric Field ◽  
Linear Trend ◽  
Limited Data ◽  
Polar Cap ◽  
Data Set ◽  
Northern Summer ◽  
Radar Network ◽  
Cross Polar Cap Potential ◽  
Hemisphere Winter ◽  
Magnetic Index

Abstract. Variation of the cross polar cap potential (CPCP) with the interplanetary electric field (IEF), the merging electric field EKL, the Polar Cap North (PCN) magnetic index, and the solar wind-magnetosphere coupling function EC of Newell et al. (2007) is investigated by considering convection data collected by the Super Dual Auroral Radar Network (SuperDARN) in the Northern Hemisphere. Winter and summer observations are considered separately. All variations considered show close to linear trend at small values of the parameters and tendency for the saturation at large values. The threshold values starting from which the non-linearity was evident were estimated to be IEF*~EKL*~3 mV/m, PCN*~3–4, and EC*~1.5×104. The data indicate that saturation starts at larger values of the above parameters and reaches larger (up to 10 kV) saturation levels during summer. Conclusions are supported by a limited data set of simultaneous SuperDARN observations in the Northern (summer) and Southern (winter) Hemispheres. It is argued that the SuperDARN CPCP saturation levels and the thresholds for the non-linearity to be seen are affected by the method of the CPCP estimates.

Greenhouses, hot water bottles, cycles and the future of New Zealand climate

2009 ◽  
pp. 61-67
Author(s):  
W.P. De Lange
Keyword(s):  
New Zealand ◽  
Thermal Energy ◽  
Infrared Radiation ◽  
Little Ice Age ◽  
Hot Water ◽  
Ice Age ◽  
The Sun ◽  
Weather Patterns ◽  
Time Periods ◽  
Almost All

The Greenhouse Effect acts to slow the escape of infrared radiation to space, and hence warms the atmosphere. The oceans derive almost all of their thermal energy from the sun, and none from infrared radiation in the atmosphere. The thermal energy stored by the oceans is transported globally and released after a range of different time periods. The release of thermal energy from the oceans modifies the behaviour of atmospheric circulation, and hence varies climate. Based on ocean behaviour, New Zealand can expect weather patterns similar to those from 1890-1922 and another Little Ice Age may develop this century.

scholarly journals Deep Learning Models for Estimation of the SuperDARN Cross Polar Cap Potential

2020 ◽  
Vol 7 (8) ◽  
Author(s):  
Erxiao Liu ◽  
Hongqiao Hu ◽  
Jianjun Liu ◽  
Lei Qiao
Keyword(s):  
Deep Learning ◽  
Learning Models ◽  
Polar Cap ◽  
Cross Polar Cap Potential

The Marine Environment

2020 ◽  
Author(s):  
Professor John Swarbrooke
Keyword(s):  
Marine Environment ◽  
Cold Water ◽  
Vital Role ◽  
Ocean Currents ◽  
The Sun ◽  
Weather Patterns ◽  
The World ◽  
Sheer Size ◽  
Almost All ◽  
Life On Earth

The fact that open ocean covers two-thirds of the surface of our planet dramati- cally illustrates the importance of the marine environment to life on Earth. But the importance of the oceans goes far beyond their sheer size for it is the oceans that largely determine our climate for the weather around the world is heavily influenced by what happens in our seas. ‘Weather patterns are primarily controlled by ocean currents which are influenced by surface winds, temperature, salinity, the Earth’s rotation and ocean tides....Ocean currents bring warm water and rain from the equator to the poles and cold water from the poles towards the equator’ (www.greentumble.com, 2016). Every schoolchild knows that the sun evaporates water from the sea which then become clouds that then produces almost all of the rain and snow which falls on every land mass in the world. The oceans also absorb heat from the sun and from human activities; this heat is then carried to the land in those places where the prevailing winds blow from the sea to the land. At the same time, the oceans play a vital role in the carbon cycle by absorbing carbon dioxide that is in the air.

scholarly journals A new formulation for the ionospheric cross polar cap potential including saturation effects

2005 ◽  
Vol 23 (11) ◽  
pp. 3533-3547 ◽  
Author(s):  
A. J. Ridley
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Mach Number ◽  
Interplanetary Magnetic Field ◽  
Polar Cap ◽  
Pressure Balance ◽  
Simple Modification ◽  
Post Shock ◽  
Cross Polar Cap Potential ◽  
New Formulation

Abstract. It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) Bz becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12mV/m at some time. When these events are examined as typically done in previous studies, all of them show some signs of saturation (i.e., over-prediction of the CPCP based on a linear relationship between the IMF and the CPCP). We show that by taking into account the size of the magnetosphere and the fact that the post-shock magnetic field strength is strongly dependent upon the solar wind Mach number, we can better specify the ionospheric CPCP. The CPCP (Φ) can be expressed as Φ=(10-4v2+11.7B(1-e-Ma/3)sin3(θ/2)) {rms/9 (where v is the solar wind velocity, B is the combined Y and Z components of the interplanetary magnetic field, Ma is the solar wind Mach number, θ=acos(Bz/B), and rms is the stand-off distance to the magnetopause, assuming pressure-balance between the solar wind and the magnetosphere). This is a simple modification of the original Boyle et al. (1997) formulation.

scholarly journals Dayside and nightside contributions to the cross polar cap potential: placing an upper limit on a viscous-like interaction

2004 ◽  
Vol 22 (10) ◽  
pp. 3771-3777 ◽  
Author(s):  
S. E. Milan
Keyword(s):  
Magnetic Flux ◽  
Polar Regions ◽  
Polar Cap ◽  
Average Decrease ◽  
The Past ◽  
Viscous Interaction ◽  
The North ◽  
Upper Limit ◽  
The Cross ◽  
Cross Polar Cap Potential

Abstract. Observations of changes in size of the ionospheric polar cap allow the dayside and nightside reconnection rates to be quantified. From these it is straightforward to estimate the rate of antisunward transport of magnetic flux across the polar regions, quantified by the cross polar cap potential ΦPC. When correlated with upstream measurements of the north-south component of the IMF, ΦPC is found to increase for more negative Bz, as expected. However, we also find that ΦPC does not, on average, decrease to zero, even for strongly northward IMF. In the past this has been interpreted as evidence for a viscous interaction between the magnetosheath flow and the outer boundaries of the magnetosphere. In contrast, we show that this is the consequence of flows excited by tail reconnection, which is inherently uncorrelated with IMF Bz.

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