UCLA Magnetometer for Ground-Based Observatory

C. T. Russell, G. Le, D. Dearborn, D. Pierce, and J. D. Means
IGPP/UCLA

Introduction

A successful array of magnetometers requires a precise low noise basic magnetometer, precise timing at each location, and a robust data system. UCLA ground-based magnetometer consists of a highly accurate fluxgate magnetometer, based on our successful magnetometers on numerous spacecraft [e.g, ISEE, PVO, POLAR] coupled to a 22 bit analogue to digital converter in a low noise electronic environment. The precise timing is provided by a GPS receiver. The data are stored temporarily on the internal disk of a Personal Computer and will be removed via portable disks from the internal disks. Utilizing a PC significantly reduces the costs per station and provides a ready source for parts and repair for a large portion of the system. The magnetic vectors are returned with a digitization of +/- 15 pT. Accurate baselines are maintained by keeping both the electronics and sensors in thermally controlled environments, isolated from other noise sources.

UCLA Gound-Based Magnetometer Design

The detail manufacturing drawings for the ground based magnetometer sensor. This sensor is designed to be installed in a post hole about 3 feet below the surface to minimize temperature effects. It includes internal heaters which can be used to further stabilize the temperature. This assembly includes:

  1. A three axis sensor assembly
  2. Heaters, thermistors, and oil filled container for temperature stabalization.
  3. The 1M tube and insulation and is attached to a 30M cable.

The Magnetometer board pictured fits a standard PC slot and has the following major sections:

  1. The GPS receiver is seen on the top far left of the board
  2. The DC/DC converter and regulators are on the bottom far left
  3. The single chip controller
  4. The precision ADC and low pass filters are under the shield near the center of the board.
  5. The Magnetometer drive/sense circuits occupy the right half of the board.

A black/white copy of the magnetometer board with a typical three axis sensor assembly. This illustrates the major components in a typical fluxgate system.

  1. Typical sensor assembly includes:
  2. Ground based Magnetometer electronics using surface mount technology.

Examples of Test Data

The top panel shows the sensor reading for applied 0.1 Hz square wave. The bottom panel shows the power spectra for the applied 0.1 Hz square wave and the noise level for zero applied field.

 

 

Applications of the UCLA Ground-Based Magnetometer

Following proposed ground magnetometer networks will use UCLA ground-based magnetometers if funded.

SMALL Array

The proposed Sino-Magnetic Array at Low Latitudes (proposed to NSF by G. Le) is a two-dimensional array across China for the study of Pi 2 magnetic pulsations and their causative substorms, the magnetospheric control of the equatorial electrojet, low latitude magnetic pulsations, and the travelling current vortices at low latitude. The sites for SMALL array are selected from existing geomagnetic observatories in China.

UC-LANL and MEASURE Networks

UC-LANL Mid-Latitude Magnetometer Network. The proposed UC-LANL Network (proposed to UC/LANL by V. Angelopoulos, G. Le and G. Reeves) consists of a 5- station northern chain (55o MLAT) and 5-stations southern chain (40o MLAT). In the proposed effort, we try to re-instate the AFGL network, a 5-station northern chain (55o MLAT) and a 2-station southern chain (40o MLAT) at Air Force base sites and complete the southern chain with five additional stations. The scientific objective is to study the magnetospheric propagation and consequences of sudden impulses (SIs), storm sudden commencements (SSCs), and substorm current wedge and Pi2 pulsations.

Magnetometers along the Eastern Atlantic Seaboard for Undergraduate Research and Education. The proposed MEASURE Network (proposed to NSF by M. Moldwin) consists of an array of closely spaced (~ 80-100 km) pairs of magnetometers at low- to mid-latitudes (L=1.7- 3.4) along the eastern Atlantic seaboard, stretching from central Florida to Ottawa, Canada. The main scientific purpose for MEASURE is to study how the wave energy is transfered to low latitudes to produce geomagnetic pulsations.

GEM Poster Session                 IGPP/SSC                 Space Physics Group