I agree that a more concise and user-friendly way to achieve this would be a nice feature to have from a user perspective. In some fields (at least the few ones that I know), these kinds of tick directions are rather common. For the record, a “recent” Gitter discussion related to the same topic occurred here.

If I see it correctly this should be simplified by the secondary_xaxis proposed in #11589, it should then look like (the API there is not yet finalized, so this is a rough estimate):

fig, ax = plt.subplots()
ax.minorticks_on()

ax_top = ax.secondary_xaxis('top', 1)
ax_top.minorticks_on()
ax_top.tick_params(which='x', direction='in', labeltop=False)

Even simpler solution would require something like proposed here.

As #11859 (note new PR number) stands now, this is:

import numpy as np
import matplotlib.pyplot as plt

convert = 1

fig, ax = plt.subplots()

ax.minorticks_on()

axsecond = ax.secondary_xaxis('top', conversion=convert)
axsecond.minorticks_on()
axsecond.tick_params(axis='x', which='both', direction='in', labeltop=False)

However if the xaxis has customized Locators and Formatters, these will not (currently) be shared with the secondary axes. Worse, I don't quite have a good API for setting the secondary axes Locators and Formatters, because they get reset every draw time to be consistent with the parent's scale (log or linear). This is a pretty big issue with #11859 at the momment, but hopefully we can work something out.

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