Downloading and plotting a HMI polar field data#

This example shows how to download HMI polar field data from JSOC and make a plot.

import matplotlib.pyplot as plt
import numpy as np

import drms

First we will create a drms.Client, using the JSOC baseurl.

client = drms.Client()

Construct the DRMS query string: “Series[timespan][wavelength]”

qstr = "hmi.meanpf_720s[2010.05.01_TAI-2016.04.01_TAI@12h]"

# Send request to the DRMS server
print("Querying keyword data...\n -> {qstr}")
result = client.query(qstr, key=["T_REC", "CAPN2", "CAPS2"])
print(f" -> {len(result)} lines retrieved.")

# Convert T_REC strings to datetime and use it as index for the series
result.index = drms.to_datetime(result.pop("T_REC"))

# Determine smallest timestep
dt = np.diff(result.index.to_pydatetime()).min()

# Make sure the time series contains all time steps (fills gaps with NaNs)
a = result.asfreq(dt)
Querying keyword data...
 -> {qstr}
 -> 4285 lines retrieved.

Plot the magnetic field values.

# Compute 30d moving average and standard deviation using a boxcar window
win_size = int(30 * 24 * 3600 / dt.total_seconds())
a_avg = a.rolling(win_size, min_periods=1, center=True).mean()
a_std = a.rolling(win_size, min_periods=1, center=True).std()

# Plot results
t = a.index.to_pydatetime()
n, mn, sn = a.CAPN2, a_avg.CAPN2, a_std.CAPN2
s, ms, ss = a.CAPS2, a_avg.CAPS2, a_std.CAPS2

# Plot smoothed data
fig, ax = plt.subplots(1, 1, figsize=(15, 7))
ax.set_title(qstr, fontsize="medium")
ax.plot(t, n, "b", alpha=0.5, label="North pole")
ax.plot(t, s, "g", alpha=0.5, label="South pole")
ax.plot(t, mn, "r", label="Moving average")
ax.plot(t, ms, "r", label="")
ax.set_xlabel("Time")
ax.set_ylabel("Mean radial field strength [G]")
ax.legend()
fig.tight_layout()

# Plot raw data
fig, ax = plt.subplots(1, 1, figsize=(15, 7))
ax.set_title(qstr, fontsize="medium")
ax.fill_between(t, mn - sn, mn + sn, edgecolor="none", facecolor="b", alpha=0.3, interpolate=True)
ax.fill_between(t, ms - ss, ms + ss, edgecolor="none", facecolor="g", alpha=0.3, interpolate=True)
ax.plot(t, mn, "b", label="North pole")
ax.plot(t, ms, "g", label="South pole")
ax.set_xlabel("Time")
ax.set_ylabel("Mean radial field strength [G]")
ax.legend()
fig.tight_layout()

plt.show()
  • hmi.meanpf_720s[2010.05.01_TAI-2016.04.01_TAI@12h]
  • hmi.meanpf_720s[2010.05.01_TAI-2016.04.01_TAI@12h]

Total running time of the script: (0 minutes 3.316 seconds)

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