Dataset Title: Open/Closed Boundary and Energy Cutoff Latitude Data for Papers 1 and 2

PI:  	David A. Smith
	Utah State University
	Department of Physics
	Logan, UT
	davidalan.smith@aggiemail.usu.edu
	(707) 834-5180

ORCID ID:  https://orcid.org/0000-0003-0370-353X

Abstract for Paper 1

The open-closed boundary (OCB) defines a region of significant transformation 
in Earth's protective magnetic shield.  Principle among these changes is the 
transition of magnetic field lines from having two foot points, one in each 
hemisphere, to one foot point at Earth, the other mapping to the solar wind (SW).  
Charged particles in the SW are able to follow these open field lines into Earth's 
upper atmosphere.  The OCB also defines the polar cap boundary (PCB).  Being able 
to identify and track the OCB allows study of several components of the 
geomagnetic system.  Among them are the electrodynamics of the geomagnetic 
field and the reconnection balance between the dayside and nightside of the 
geomagnetic field.  Furthermore, the OCB can provide interesting insights into 
the precipitation of energetic protons into the ionosphere.  Using the Tsyganenko 
model of the geomagnetic field we demonstrate a diurnal fluctuation which we call 
the Universal Time (UT) effect of the OCB.  This UT effect is independent of all 
other inputs.  We anticipate this UT effect to have important consequences in modeling 
the OCB and other polar cap-associated structures, especially polar cap absorption (PCA) 
events which adversely affect high frequency radio wave propagation  in polar regions.

Abstract for Paper 2:

The first well-documented polar cap absorption event occurred on 23 February 1956.  
Since that time much has been learned and explored regarding these events and their 
effect on high-frequency radio wave propagation in earth's polar regions.  An important 
boundary when considering geomagnetic field topology and polar cap absorption events is 
commonly referred to as the cutoff latitude or energy cutoff latitude.  The cutoff latitude 
is dependent on several factors, including solar wind parameters and proton energy.  There 
exists an extensive body of research involving the cutoff latitude.  One common approach in 
finding the cutoff latitude is to use a model of the geomagnetic field and trace proton 
trajectories through the field.  Using this approach and the 1996 version of the Tsyganenko 
model, we demonstrate a unique method to organize three cutoff latitude boundary dependencies.  
The first, which we call a Universal Time or UT effect, is independent of proton energy and 
is based on geomagnetic alignment.  The second, a local time or LT effect, exhibits an 
energy-dependent modulation as well as solar wind dependence.  The third, a longitudinal 
effect, is also energy-dependent.  Together, these effects can significantly alter the solar 
proton energy cutoff latitude, especially in the energy regime most responsible for polar 
cap absorption events.    

Data Collection:

The data were collected using the Tsyganenko Model of the Geomagnetic field, freely
available at the CCMC.  We used our own FORTRAN code in conjunctions with the T96 model
to determine the OCB as well as the cutoff latitude for various proton energies.

File Name Formatting

The first letter indicates the proton energy level and the second indicates the geomagnetic
activity level. There are 9 energy levels, so the letters A-I indicate energy levels 1-100 MeV
as described in the text.

A=1.00 MeV
B=1.78 MeV
C=3.16
D=5.62
E=10.0
F=17.8
G=31.6
H=56.2
I=100

Q=Quiet conditions
M=Moderate conditions
S=severe conditions

Hence, the file AQ contains the data for 1.00 MeV protons during quiet conditions.

Column Headings:

The data for each geomagnetic storm condition (quiet, moderate, severe) are contained
in files for each energy bin (1.00, 1.78, 3.16, etc MeV).  Each file contains 24 sets or blocks
of data arranged in 7 columns each.  Each block consists of the following column headings:

Geographical Longitude
Universal Time
Local Time
Geographic Latitude of OCB
Magnetic Latitude of OCB
Geographic Latitude of Cutoff Latitude
Magnetic Latitude of Cutoff Latitude

It should be readily apparent when examining a file that each block is for a constant
UT.  Hence, all 24 rows for each UT block will show a constant UT. Generally the files
are arranged such that LT runs from 0-24, but this is not always the case.  It should be
apparent on a case-by-case basis.

It should also be apparent that the OCB latitudes are consistent across energy bins, since
the OCB is not energy dependent.