IFE-Dust-Source

Overview of Theory

Interplanetary Field Enhancements (IFEs) were first discovered within the Venusian orbit and were believed to be generated by charged dust mass-loading interplanetary magnetic fields, originally the asteroid 2201 Oljato (Russell 1987). However, the dust source hypothesis for IFEs remains a controversial stance. This program will attempt to correlate IFEs measured near-Earth in the solar wind to small bodies which could be a source of dust.

A strong candidate dust source will be a small body that has an orbit inclination close to the XY plane (GSE) of the spacecraft and be the region around the time the IFEs were found (i.e. have a small phase difference) for multiple orbits. Because of the large gyroradius of the charged dust, the cloud will travel approximately radially from the source.

We will first identify possible dust sources for each event and then compare subsequent periods of the small bodies identified to find the percentage of the time IFEs are again seen (see below). Note the periods that can be tested will be constrained by the on the orbital inclination of the body.

We will consider a small phase difference as anything less than 20 degrees approaching and retreating. We will consider the orbital inclination to be close from an average radial size of IFEs in the XY plane (GSE).

Subsequent statistically analysis will be performed through the entire orbit of promising dust source candidates on how the frequency of IFEs changes at different points in the body's orbit (see Russell 1987).

Dust Theory

Dust is produced via numerous collisions with asteroids and comets, which gets photoionized rapidly. Charged particles mass-load the incident magnetic field, create a pile-up (increasing |B|). The resulting bend of the magnetic field around the obstacle generates a force that accelerates the dust cloud away from the sun. This disturbance is seen as an IFE.

Overview of Code

neo_asteroid_features_from_date_to_date.csv will contain all the information for each asteroid (diameter, inclination, etc.)

NASA API Details

"NeoWs (Near Earth Object Web Service) is a RESTful web service for near earth Asteroid information. With NeoWs a user can: search for Asteroids based on their closest approach date to Earth, lookup a specific Asteroid with its NASA JPL small body id, as well as browse the overall data-set.

Data-set: All the data is from the NASA JPL Asteroid team"

Definitions of Variables

• e = eccentricity (no unit) describes how close the orbit is to a perfect circle (0 = circle, 0-1 = elliptical orbit, 1 = parabolic escape, >1 = hyperbola)
• a = semi-major axis (Au) describes the long axis of the ellipitical orbit
• i = inclination (degree) describes the angle with respect to the xy ecliptic plane
• peri = argument of perihelion (degree) describes the angle between the orbiting body's closest approach to Earth and its ascending node
• t_p = (TDB: Barycentric Dynamical Time) describes the time when the orbiting body last passed its closest approach
• n = mean motion (deg/day) describes the reciprocal of the period
• Q = aphelion distance (Au) describes the point furthest from the sun in its orbit
• period = sidereal orbit period (day & year) describes the time for one orbit
• M = mean anomaly (deg) describes the fraction of an elliptical orbit's period elapsed since passing the closest approach
• node = longitude of the ascending node (degree) describes the angle in the xy ecliptic plane from a reference longitude around the sun to the point in the orbit where the body rises through the ecliptic
• q = perihelion distance (Au) describes the point in the orbit closest to the sun

Restrictions

IFEs have a short time before they have been accelerated up to solar wind velocity and dissapear. Therefore, we will only consider events whose passage into the orbital range of interest occur within 1/10 of an Au of Earth.

Simplifying Assumptions

1. The radius of all IFEs is assumed to be the average radial scale length of IFEs (for ACE this is around 1.7e+06 km)
2. All relevant small bodies are listed in the NASA Small Body JPL collection

Orbital Timing

We are concerned with the time the orbiting body spends above/below the xy ecliptic plane. To find this we need to find the time it takes for the body to travel from perihelion (crosses at t_p) to the ascending node (t_A). The time when the body is above the ecliptic plane but within the radius of the IFE is given by t_N.

Run Code

python pre_processing.py -A DEMO_KEY -P True -D Date-File.csv

Parameters:

-A

API_KEY (Note: Can use 'DEMO_KEY' for a test run)

-P

Options: True or False

To print details to Command Line (Default set to False)

-D

CSV date file for identified IFEs

TODO

1. Strip position for ACE in J200 from Cdaweb and for Small Body from Horizons
2. Compare with the position of low-Earth orbit satellites detecting IFEs